Refacor electron app and add migrations

electron/cqrs/commands/handlers/removeReaction.ts

@@ -0,0 +1,10 @@
+import { DataSource } from 'typeorm';
+import { ReactionEntity } from '../../../entities';
+import { RemoveReactionCommand } from '../../types';
+
+export async function handleRemoveReaction(command: RemoveReactionCommand, dataSource: DataSource): Promise<void> {
+  const repo = dataSource.getRepository(ReactionEntity);
+  const { messageId, userId, emoji } = command.payload;
+
+  await repo.delete({ messageId, userId, emoji });
+}