chore(legacy): relocate v1 dataconnect source

legacy/dataconnect-v1/schema/userConversation.gql

@@ -0,0 +1,17 @@
+type UserConversation @table(name: "user_conversations", key: ["conversationId", "userId"]) {
+  id: UUID! @default(expr: "uuidV4()")
+
+  conversationId: UUID!
+  conversation: Conversation! @ref(fields: "conversationId", references: "id")
+
+  userId: String!
+  user: User! @ref(fields: "userId", references: "id")
+
+  # per-user state
+  unreadCount: Int @default(expr: "0")
+  lastReadAt: Timestamp
+
+  createdAt: Timestamp @default(expr: "request.time")
+  updatedAt: Timestamp @default(expr: "request.time")
+  createdBy: String
+}