Extract CountAttendeesByEventUseCase to decouple controller from repository

The EventController was directly accessing RsvpRepository (an outbound port)
to count attendees, bypassing the application layer. Introduce a dedicated
inbound port and implement it in RsvpService. Remove the now-unused Clock
dependency from RsvpService.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/main/java/de/fete/adapter/in/web/EventController.java

@@ -12,10 +12,10 @@ import de.fete.domain.model.CreateEventCommand;
 import de.fete.domain.model.Event;
 import de.fete.domain.model.EventToken;
 import de.fete.domain.model.Rsvp;
+import de.fete.domain.port.in.CountAttendeesByEventUseCase;
 import de.fete.domain.port.in.CreateEventUseCase;
 import de.fete.domain.port.in.CreateRsvpUseCase;
 import de.fete.domain.port.in.GetEventUseCase;
-import de.fete.domain.port.out.RsvpRepository;
 import java.time.Clock;
 import java.time.DateTimeException;
 import java.time.LocalDate;
@@ -32,20 +32,20 @@ public class EventController implements EventsApi {
   private final CreateEventUseCase createEventUseCase;
   private final GetEventUseCase getEventUseCase;
   private final CreateRsvpUseCase createRsvpUseCase;
-  private final RsvpRepository rsvpRepository;
+  private final CountAttendeesByEventUseCase countAttendeesByEventUseCase;
   private final Clock clock;
 
-  /** Creates a new controller with the given use cases, repository, and clock. */
+  /** Creates a new controller with the given use cases and clock. */
   public EventController(
       CreateEventUseCase createEventUseCase,
       GetEventUseCase getEventUseCase,
       CreateRsvpUseCase createRsvpUseCase,
-      RsvpRepository rsvpRepository,
+      CountAttendeesByEventUseCase countAttendeesByEventUseCase,
       Clock clock) {
     this.createEventUseCase = createEventUseCase;
     this.getEventUseCase = getEventUseCase;
     this.createRsvpUseCase = createRsvpUseCase;
-    this.rsvpRepository = rsvpRepository;
+    this.countAttendeesByEventUseCase = countAttendeesByEventUseCase;
     this.clock = clock;
   }
 
@@ -90,7 +90,7 @@ public class EventController implements EventsApi {
     response.setTimezone(event.getTimezone().getId());
     response.setLocation(event.getLocation());
     response.setAttendeeCount(
-        (int) rsvpRepository.countByEventId(event.getId()));
+        (int) countAttendeesByEventUseCase.countByEvent(eventToken));
     response.setExpired(
         event.getExpiryDate().isBefore(LocalDate.now(clock)));
 

backend/src/main/java/de/fete/application/service/RsvpService.java

@@ -4,28 +4,25 @@ import de.fete.domain.model.Event;
 import de.fete.domain.model.EventToken;
 import de.fete.domain.model.Rsvp;
 import de.fete.domain.model.RsvpToken;
+import de.fete.domain.port.in.CountAttendeesByEventUseCase;
 import de.fete.domain.port.in.CreateRsvpUseCase;
 import de.fete.domain.port.out.EventRepository;
 import de.fete.domain.port.out.RsvpRepository;
-import java.time.Clock;
 import org.springframework.stereotype.Service;
 
 /** Application service implementing RSVP creation. */
 @Service
-public class RsvpService implements CreateRsvpUseCase {
+public class RsvpService implements CreateRsvpUseCase, CountAttendeesByEventUseCase {
 
   private final EventRepository eventRepository;
   private final RsvpRepository rsvpRepository;
-  private final Clock clock;
 
   /** Creates a new RsvpService. */
   public RsvpService(
       EventRepository eventRepository,
-      RsvpRepository rsvpRepository,
-      Clock clock) {
+      RsvpRepository rsvpRepository) {
     this.eventRepository = eventRepository;
     this.rsvpRepository = rsvpRepository;
-    this.clock = clock;
   }
 
   @Override
@@ -40,4 +37,11 @@ public class RsvpService implements CreateRsvpUseCase {
 
     return rsvpRepository.save(rsvp);
   }
+
+  @Override
+  public long countByEvent(EventToken eventToken) {
+    Event event = eventRepository.findByEventToken(eventToken)
+        .orElseThrow(() -> new EventNotFoundException(eventToken.value()));
+    return rsvpRepository.countByEventId(event.getId());
+  }
 }

backend/src/main/java/de/fete/domain/port/in/CountAttendeesByEventUseCase.java

@@ -0,0 +1,10 @@
+package de.fete.domain.port.in;
+
+import de.fete.domain.model.EventToken;
+
+/** Inbound port for counting attendees of an event. */
+public interface CountAttendeesByEventUseCase {
+
+  /** Counts the number of confirmed attendees for the given event. */
+  long countByEvent(EventToken eventToken);
+}