Implemented the second round of the toResponse normalisationf for all classes

ref #67

src/models/entities/GroupContact.ts

@@ -81,4 +81,11 @@ export class GroupContact implements IAddressUser {
     */
   @OneToMany(() => RunnerGroup, group => group.contact, { nullable: true })
   groups: RunnerGroup[];
+
+  /**
+   * Turns this entity into it's response class.
+   */
+  public toResponse() {
+    return new Error("NotImplemented");
+  }
 }