Implemented a possible bugfix

ref #68

src/models/entities/GroupContact.ts

@@ -10,6 +10,7 @@ import {
 import { Column, Entity, ManyToOne, OneToMany, PrimaryGeneratedColumn } from "typeorm";
 import { config } from '../../config';
 import { Address } from "./Address";
+import { IAddressUser } from './IAddressUser';
 import { RunnerGroup } from "./RunnerGroup";
 
 /**
@@ -17,7 +18,7 @@ import { RunnerGroup } from "./RunnerGroup";
  * Mainly it's own class to reduce duplicate code and enable contact's to be associated with multiple groups.
 */
 @Entity()
-export class GroupContact {
+export class GroupContact implements IAddressUser {
   /**
    * Autogenerated unique id (primary key).
    */
@@ -54,7 +55,7 @@ export class GroupContact {
    * This is a address object to prevent any formatting differences.
    */
   @IsOptional()
-  @ManyToOne(() => Address, address => address.participants, { nullable: true })
+  @ManyToOne(() => Address, address => address.addressUsers, { nullable: true })
   address?: Address;
 
   /**