API-23: Refactoring for better architecture (#12)

Endpoints are separated into distinct packages and interfaces are extracted into files

Co-authored-by: Patrick Müller <patrick@mueller-patrick.tech>
Reviewed-on: #12
Co-authored-by: Patrick Müller <patrick@plutodev.de>
Co-committed-by: Patrick Müller <patrick@plutodev.de>

src/models/partyplaner/event/Event.interface.ts

@@ -0,0 +1,16 @@
+import {Invite} from './Invite.interface';
+import {Registration} from './Registration.interface';
+
+/**
+ * Used in the getEventData method as a return value
+ */
+export interface Event {
+    eventId: string;
+    name: string;
+    description: string;
+    takesPlaceDate: Date;
+    registrationUntilDate: Date;
+    maxParticipants: number;
+    invites: Invite[];
+    registrations: Registration[];
+}