Refacor electron app and add migrations

electron/cqrs/queries/handlers/getAllAttachments.ts

@@ -0,0 +1,10 @@
+import { DataSource } from 'typeorm';
+import { AttachmentEntity } from '../../../entities';
+import { rowToAttachment } from '../../mappers';
+
+export async function handleGetAllAttachments(dataSource: DataSource) {
+  const repo = dataSource.getRepository(AttachmentEntity);
+  const rows = await repo.find();
+
+  return rows.map(rowToAttachment);
+}