feat(base,app)!: GitHub signs nobody in any more (ADR 0020, D36)

Every account signs in with SimpleLogin or a password now, so GitHub
goes from the module, the shared app package, Learn and Todo, ahead of
ADR 0017's GITHUB_SIGN_IN_ENDS.

- halkyon_base: no `gitHubSignIn` endpoint, GitHub identity provider or
  GitHub refusals; no `githubClientId`/`githubClientSecret`, no
  `GITHUB_SIGN_IN_ENDS` and no `forgetGitHubAccounts`; the register
  loses `account-with-github`. `SignInWays.gitHub`, the basics'
  `gitHubClientId` and `gitHubSignInEnds`, and `PasswordRefusal`'s
  `signInAgain` and `noAddress` go. A first password takes a code
  mailed to the person's own address; an account without one sets none
  (`wrongCredentials`).
- Learn's server: `instance.info()` without `gitHubClientId`, the
  pruning without GitHub, and `minimumAppBuild` 24, as builds up to 23
  (v0.20.0) require `SignInWays.gitHub`: the server deploys with the
  release of build 24.
- halkyon_app: no GitHub button or problems on the start screen, no
  password offered after a GitHub sign-in, and `ServerpodAuthGateway`
  without the browser half only GitHub used (`(client, base:)`). The
  account section offers a first password only to an account with an
  address. `LoopbackWebAuth` and the apps' schemes stay, SimpleLogin's
  ways back.
- Learn's Profile lists no GitHub; the texts go (English, German).
- Serverpod's `serverpod_auth_idp_github_account` stays, as its
  migrations make it; a row goes with its account, and ADR 0020's D36
  gives operators the SQL to delete those left.
- deploy/: compose.yaml and .env.example without GitHub. The READMEs,
  AGENTS.md files and ADR 0017 amended.

BREAKING CHANGE: builds up to 23 can't read the instance's answers
about an account's ways in; minimumAppBuild is 24.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/learn/halkyon_learn_flutter/test/feature/auth/widget/password_set_up_test.dart

@@ -47,10 +47,13 @@ void main() {
     await tester.pumpAndSettle();
   }
 
-  testWidgets('an account without a password sets one up: the address, the '
-      'phrase checked, the handle it lacks, the code, the authenticator', (
-    tester,
-  ) async {
+  testWidgets('an account with an address and no password sets one up: the '
+      'address, the phrase checked, the handle it lacks, the code, the '
+      'authenticator', (tester) async {
+    passwords.addAddressOnly(
+      'anna@example.org',
+      person: FakeAuthGateway.person.authUserId,
+    );
     await openProfile(tester);
 
     await tester.tap(find.text('Set up a password'));
@@ -105,28 +108,6 @@ void main() {
     expect(find.text('Change password'), findsOneWidget);
   });
 
-  testWidgets('someone who signs in with GitHub is told when it ends, and '
-      'offered a password', (tester) async {
-    auth = FakeAuthGateway(
-      status: const SignedIn(authUserId: 'github-person', isIdentified: true),
-    )..gitHubPeople.add('github-person');
-    passwords = FakePasswordGateway(auth)
-      ..gitHubPeople.add('github-person')
-      ..gitHubEnds = DateTime.utc(2027, 1, 22);
-    await openProfile(tester);
-
-    expect(find.textContaining('Sign-in with GitHub ends on'), findsOneWidget);
-    // Without an address, the account goes 30 days after the end (the full
-    // reading's M1, the short reading's day).
-    expect(
-      find.textContaining(
-        'an account without one is deleted 30 days later, with everything',
-      ),
-      findsOneWidget,
-    );
-    expect(find.text('Set up a password'), findsOneWidget);
-  });
-
   testWidgets('no password where the instance offers none', (tester) async {
     passwords.offered = false;
 

apps/learn/halkyon_learn_flutter/test/feature/auth/widget/profile_account_test.dart

@@ -5,8 +5,8 @@ import '../../../support/pump_app.dart';
 import '../../../support/test_dependencies.dart';
 
 // The Profile tab's account card: the ways the person signs in, SimpleLogin
-// to add (ADR 0020, D21) and nothing else to add, as GitHub is added to
-// nobody any more (D25).
+// to add (ADR 0020, D21) and nothing else to add, as GitHub signs nobody in
+// any more (D36).
 void main() {
   late FakeAuthGateway auth;
   late FakeSimpleLoginGateway simpleLogin;
@@ -33,20 +33,8 @@ void main() {
     );
   });
 
-  testWidgets('an account with GitHub sees it signs them in, with nothing to '
-      'add', (tester) async {
-    auth.gitHubPeople.add(FakeAuthGateway.person.authUserId);
-
-    await openProfile(tester);
-
-    expect(find.text('GitHub'), findsOneWidget);
-    expect(find.text('Signs you in'), findsWidgets);
-    expect(find.text('Add GitHub'), findsNothing);
-  });
-
-  testWidgets('an account without GitHub is offered none to add (D25)', (
-    tester,
-  ) async {
+  testWidgets('an account lists its address, and no GitHub to have or add '
+      '(D36)', (tester) async {
     auth.addressOwners['ada@example.org'] = FakeAuthGateway.person.authUserId;
 
     await openProfile(tester);

apps/learn/halkyon_learn_flutter/test/feature/auth/widget/session_widgets_test.dart

@@ -90,47 +90,14 @@ void main() {
     expect(find.text('Start on learn.example.org:'), findsOneWidget);
     expect(find.text('Sign in'), findsOneWidget);
     expect(find.text('Create an account'), findsOneWidget);
-    expect(find.text('Sign in with GitHub'), findsOneWidget);
+    expect(
+      find.textContaining('GitHub'),
+      findsNothing,
+      reason: 'GitHub signs nobody in any more (ADR 0020, D36)',
+    );
     expect(find.text('Start without an account'), findsNothing);
   });
 
-  testWidgets('from there, GitHub signs in its person', (tester) async {
-    await signOut(tester);
-
-    await tester.tap(find.text('Sign in with GitHub'));
-    await tester.pumpAndSettle();
-    // A password is offered first (ADR 0017, D2); put off, the app.
-    await tester.tap(find.text('Later'));
-    await tester.pumpAndSettle();
-
-    expect(
-      gateway.status,
-      const SignedIn(authUserId: 'github-person', isIdentified: true),
-    );
-    expect(home, findsOneWidget);
-  });
-
-  testWidgets('from there, a GitHub account nobody here signs in with is said '
-      'so, with an account to create in its place where passwords are '
-      'offered (ADR 0017)', (tester) async {
-    await signOut(tester);
-
-    gateway.gitHubError = const GitHubSignInFailed(
-      GitHubSignInProblem.unknownAccount,
-    );
-    await tester.tap(find.text('Sign in with GitHub'));
-    await tester.pumpAndSettle();
-
-    expect(
-      find.text(
-        'No account here signs in with this GitHub account. Create an '
-        'account with your email address and a password instead.',
-      ),
-      findsOneWidget,
-    );
-    expect(gateway.status, const SignedOut());
-  });
-
   testWidgets('where an instance offers no way to make an account, it says '
       'so', (tester) async {
     await signOut(tester, passwords: false);

apps/learn/halkyon_learn_flutter/test/feature/discussion/discussion_widgets_test.dart

@@ -34,7 +34,7 @@ void main() {
       testDependencies(
         authGateway: FakeAuthGateway(
           status: const SignedIn(
-            authUserId: 'github-person',
+            authUserId: 'person-2',
             isIdentified: true,
           ),
         ),

apps/learn/halkyon_learn_flutter/test/feature/explore/explore_screen_test.dart

@@ -107,7 +107,7 @@ void main() {
       testDependencies(
         authGateway: FakeAuthGateway(
           status: const SignedIn(
-            authUserId: 'github-person',
+            authUserId: 'person-2',
             isIdentified: true,
           ),
         ),

apps/learn/halkyon_learn_flutter/test/feature/feedback/feedback_widgets_test.dart

@@ -101,7 +101,7 @@ void main() {
       testDependencies(
         authGateway: FakeAuthGateway(
           status: const SignedIn(
-            authUserId: 'github-person',
+            authUserId: 'person-2',
             isIdentified: true,
           ),
         ),

apps/learn/halkyon_learn_flutter/test/feature/profile/public_profile_test.dart

@@ -38,7 +38,7 @@ void main() {
       testDependencies(
         authGateway: FakeAuthGateway(
           status: const SignedIn(
-            authUserId: 'github-person',
+            authUserId: 'person-2',
             isIdentified: true,
           ),
         ),

apps/learn/halkyon_learn_flutter/test/feature/publish/publish_sheet_test.dart

@@ -74,7 +74,7 @@ void main() {
       testDependencies(
         authGateway: FakeAuthGateway(
           status: const SignedIn(
-            authUserId: 'github-person',
+            authUserId: 'person-2',
             isIdentified: true,
           ),
         ),

apps/learn/halkyon_learn_flutter/test/feature/studyset/widget/studyset_screen_test.dart

@@ -1872,10 +1872,8 @@ void main() {
     expect(find.text('Japanese'), findsNothing);
     expect(find.text('Start on learn.example.org:'), findsOneWidget);
 
-    await tester.tap(find.text('Sign in with GitHub'));
-    await tester.pumpAndSettle();
-    // A password is offered first (ADR 0017, D2); put off, the app.
-    await tester.tap(find.text('Later'));
+    // Another person signs in, as a sign-in's session put in place does it.
+    auth.signIn('person-2');
     await tester.pumpAndSettle();
 
     expect(find.text('Japanese'), findsNothing);