chore(backend): Setup MikroORM

Simpele configuratie, geen integratie
Succesvol commando's uitvoeren werkt

backend/src/entities/user.entity.ts

@@ -0,0 +1,13 @@
+import { Entity, OneToOne, PrimaryKey, Property } from '@mikro-orm/core'
+
+@Entity()
+export class User {
+  @PrimaryKey({ type: 'number' })
+  id!: number;
+
+  @Property()
+  firstName: string = '';
+
+  @Property()
+  lastName: string = '';
+}