Added relations to RunnerGroup

ref #11

src/models/GroupContact.ts

@@ -1,8 +1,15 @@
-import { Entity } from "typeorm";
+import { Entity, OneToMany } from "typeorm";
 import { Participant } from "./Participant";
+import { RunnerGroup } from "./RunnerGroup";
 
 /**
  * Defines a group's contact.
 */
 @Entity()
-export class GroupContact extends Participant{}
+export class GroupContact extends Participant{
+  /**
+    * Used to link runners to donations.
+    */
+  @OneToMany(() => RunnerGroup, group => group.contact)
+  groups: RunnerGroup[];
+}