Refacor electron app and add migrations

electron/cqrs/queries/handlers/getMessages.ts

@@ -0,0 +1,17 @@
+import { DataSource } from 'typeorm';
+import { MessageEntity } from '../../../entities';
+import { GetMessagesQuery } from '../../types';
+import { rowToMessage } from '../../mappers';
+
+export async function handleGetMessages(query: GetMessagesQuery, dataSource: DataSource) {
+  const repo = dataSource.getRepository(MessageEntity);
+  const { roomId, limit = 100, offset = 0 } = query.payload;
+  const rows = await repo.find({
+    where: { roomId },
+    order: { timestamp: 'ASC' },
+    take: limit,
+    skip: offset
+  });
+
+  return rows.map(rowToMessage);
+}