feat(guild-messaging): switch seq allocation to DB transaction with row lock

Fabric.Backend.Guild/src/messaging/messaging.module.ts

@@ -1,7 +1,11 @@
 import { Module } from '@nestjs/common';
+import { TypeOrmModule } from '@nestjs/typeorm';
 import { MessagingController } from './messaging.controller';
+import { Channel } from '../entities/channel.entity';
+import { Message } from '../entities/message.entity';
 
 @Module({
+  imports: [TypeOrmModule.forFeature([Channel, Message])],
   controllers: [MessagingController],
 })
 export class MessagingModule {}