Cleaned up a load of relations and optional stuff

ref #11

src/models/entities/Donation.ts

@@ -1,7 +1,6 @@
 import {
   IsInt,
-  IsNotEmpty,
-  IsOptional
+  IsNotEmpty
 } from "class-validator";
 import { Entity, ManyToOne, PrimaryGeneratedColumn, TableInheritance } from "typeorm";
 import { Participant } from "./Participant";
@@ -16,7 +15,6 @@ export abstract class Donation {
    * Autogenerated unique id (primary key).
    */
   @PrimaryGeneratedColumn()
-  @IsOptional()
   @IsInt()
   id: number;
 
@@ -24,7 +22,7 @@ export abstract class Donation {
    * The donations's donor.
    */
   @IsNotEmpty()
-  @ManyToOne(() => Participant, donor => donor.donations, { nullable: true })
+  @ManyToOne(() => Participant, donor => donor.donations)
   donor: Participant;
 
   /**