Move stubs from ./stubs to ./shared/Stubs

Gathers all shared test code in single place.

tests/unit/shared/Stubs/NumericEntityStub.ts

@@ -0,0 +1,14 @@
+import { BaseEntity } from '@/infrastructure/Entity/BaseEntity';
+
+export class NumericEntityStub extends BaseEntity<number> {
+  public customProperty = 'customProperty';
+
+  public constructor(id: number) {
+    super(id);
+  }
+
+  public withCustomProperty(value: string): NumericEntityStub {
+    this.customProperty = value;
+    return this;
+  }
+}