refactor: prepare code for more than one database

package.json

@@ -10,7 +10,8 @@
     "start": "electron .",
     "dev": "electron . --enable-logging",
     "rebuild": "electron-rebuild -f -b -t prod,dev,optional",
-    "typeorm:migrate": "typeorm migration:run -c library",
+    "typeorm:migrate": "npm run typeorm:migrate:library",
+    "typeorm:migrate:library": "typeorm migration:run -c library",
     "tsc": "gulp tsc:watch",
     "webpack": "webpack --watch",
     "eslint-check": "eslint --print-config . | eslint-config-prettier-check",

src/main/services/database.ts

@@ -1,7 +1,7 @@
 import 'reflect-metadata';
 import { Connection, createConnection } from 'typeorm';
 
-let connection: Connection;
+export let library: Connection;
 
 function init(): void {
   initConnection();
@@ -12,7 +12,7 @@ function initConnection(): void {
   // from your ormconfig file or environment variables
   createConnection('library')
     .then((c: Connection) => {
-      connection = c;
+      library = c;
     })
     .catch((reason: any) => {
       throw reason;