feat: Implement merge changes method (#38)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Marcelo Soares <marcelo.me.soares@gmail.com>

packages/serverpod_offline_sync_server/lib/src/models/merge/change.spy.yaml

@@ -0,0 +1,13 @@
+### A remote CRDT change to merge.
+class: CrdtMergeChange
+sealed: true
+extends: BaseHlc
+fields:
+  ### The table receiving the change.
+  tableName: String
+
+  ### The domain row identifier receiving the change.
+  uuidRowId: UuidValue
+
+  ### The remote node that produced the change.
+  uuidNodeId: UuidValue

packages/serverpod_offline_sync_server/lib/src/models/merge/delete.spy.yaml

@@ -0,0 +1,6 @@
+### A remote tombstone update to merge.
+class: CrdtMergeDelete
+extends: CrdtMergeChange
+fields:
+  ### Whether the row is deleted or restored.
+  isDeleted: bool

packages/serverpod_offline_sync_server/lib/src/models/merge/insert.spy.yaml

@@ -0,0 +1,6 @@
+### A remote row insertion to merge.
+class: CrdtMergeInsert
+extends: CrdtMergeChange
+fields:
+  ### The serialized domain row payload for the insert.
+  data: dynamic

packages/serverpod_offline_sync_server/lib/src/models/merge/set.spy.yaml

@@ -0,0 +1,11 @@
+### A set of remote CRDT changes to merge into the local database.
+class: CrdtMergeSet
+fields:
+  ### Remote row insertions.
+  inserts: List<CrdtMergeInsert>
+
+  ### Remote field updates.
+  updates: List<CrdtMergeUpdate>
+
+  ### Remote tombstone updates.
+  deletes: List<CrdtMergeDelete>

packages/serverpod_offline_sync_server/lib/src/models/merge/update.spy.yaml

@@ -0,0 +1,9 @@
+### A remote field update to merge.
+class: CrdtMergeUpdate
+extends: CrdtMergeChange
+fields:
+  ### The updated database column name.
+  columnName: String
+
+  ### The serialized new value for the column.
+  value: dynamic