feat(server): runtime setting support (#5602)

---

<details open="true"><summary>Generated summary (powered by <a href="https://app.graphite.dev">Graphite</a>)</summary>

> ## TL;DR
> This pull request adds a new migration file, a new model, and new modules related to runtime settings. It also introduces a new `Runtime` service that allows getting, setting, and updating runtime configurations.
>
> ## What changed
> - Added a new migration file `migration.sql` that creates a table called `application_settings` with columns `key` and `value`.
> - Added a new model `ApplicationSetting` with properties `key` and `value`.
> - Added a new module `RuntimeSettingModule` that exports the `Runtime` service.
> - Added a new service `Runtime` that provides methods for getting, setting, and updating runtime configurations.
> - Modified the `app.module.ts` file to import the `RuntimeSettingModule`.
> - Modified the `index.ts` file in the `fundamentals` directory to export the `Runtime` service.
> - Added a new file `def.ts` in the `runtime` directory that defines the runtime configurations and provides a default implementation.
> - Added a new file `service.ts` in the `runtime` directory that implements the `Runtime` service.
>
> ## How to test
> 1. Run the migration script to create the `application_settings` table.
> 2. Use the `Runtime` service to get, set, and update runtime configurations.
> 3. Verify that the runtime configurations are stored correctly in the database and can be retrieved and modified using the `Runtime` service.
>
> ## Why make this change
> This change introduces a new feature related to runtime settings. The `Runtime` service allows the application to dynamically manage and modify runtime configurations without requiring a restart. This provides flexibility and allows for easier customization and configuration of the application.
</details>

packages/backend/server/src/core/sync/events/events.gateway.ts

@@ -11,7 +11,7 @@ import {
 import { Server, Socket } from 'socket.io';
 import { encodeStateAsUpdate, encodeStateVector } from 'yjs';
 
-import { CallTimer, metrics } from '../../../fundamentals';
+import { CallTimer, Config, metrics } from '../../../fundamentals';
 import { Auth, CurrentUser } from '../../auth';
 import { DocManager } from '../../doc';
 import { DocID } from '../../utils/doc';
@@ -98,6 +98,7 @@ export class EventsGateway implements OnGatewayConnection, OnGatewayDisconnect {
   private connectionCount = 0;
 
   constructor(
+    private readonly config: Config,
     private readonly docManager: DocManager,
     private readonly permissions: PermissionService
   ) {}
@@ -115,10 +116,13 @@ export class EventsGateway implements OnGatewayConnection, OnGatewayDisconnect {
     metrics.socketio.gauge('realtime_connections').record(this.connectionCount);
   }
 
-  assertVersion(client: Socket, version?: string) {
+  async assertVersion(client: Socket, version?: string) {
+    const shouldCheckClientVersion = await this.config.runtime.fetch(
+      'flags/syncClientVersionCheck'
+    );
     if (
       // @todo(@darkskygit): remove this flag after 0.12 goes stable
-      AFFiNE.featureFlags.syncClientVersionCheck &&
+      shouldCheckClientVersion &&
       version !== AFFiNE.version
     ) {
       client.emit('server-version-rejected', {
@@ -180,7 +184,7 @@ export class EventsGateway implements OnGatewayConnection, OnGatewayDisconnect {
     @MessageBody('version') version: string | undefined,
     @ConnectedSocket() client: Socket
   ): Promise<EventResponse<{ clientId: string }>> {
-    this.assertVersion(client, version);
+    await this.assertVersion(client, version);
     await this.assertWorkspaceAccessible(
       workspaceId,
       user.id,
@@ -203,7 +207,7 @@ export class EventsGateway implements OnGatewayConnection, OnGatewayDisconnect {
     @MessageBody('version') version: string | undefined,
     @ConnectedSocket() client: Socket
   ): Promise<EventResponse<{ clientId: string }>> {
-    this.assertVersion(client, version);
+    await this.assertVersion(client, version);
     await this.assertWorkspaceAccessible(
       workspaceId,
       user.id,