merge : #151 행사 같이 가고 싶어요 등록 해제 api 구현

backend/emm-sale/src/docs/asciidoc/index.adoc

@@ -133,6 +133,14 @@ include::{snippets}/participate-event/http-request.adoc[]
 .HTTP response
 include::{snippets}/participate-event/http-response.adoc[]
 
+=== `DELETE` : 컨퍼런스에 함께가기 요청 취소(컨퍼런스에 함께 가는 멤버에서 삭제)
+
+.HTTP request
+include::{snippets}/participate-event-cancel/http-request.adoc[]
+
+.HTTP response
+include::{snippets}/participate-event-cancel/http-response.adoc[]
+
 === `GET`: 행사 목록 조회
 
 .HTTP request

backend/emm-sale/src/main/java/com/emmsale/event/api/EventApi.java

@@ -46,17 +46,24 @@ public ResponseEntity<String> participateEvent(
       @RequestBody final EventParticipateRequest request,
       final Member member
   ) {
-    final Long participantId = eventService.participate(
-        eventId,
-        request.getMemberId(),
-        member
-    );
+    final Long participantId = eventService.participate(eventId, request.getMemberId(), member);
 
     return ResponseEntity
         .created(create(format("/events/%s/participants/%s", eventId, participantId)))
         .build();
   }
 
+  @DeleteMapping("/{eventId}/participants")
+  public ResponseEntity<String> cancelParticipateEvent(
+      @PathVariable final Long eventId,
+      @RequestBody final EventParticipateRequest request,
+      final Member member
+  ) {
+    eventService.cancelParticipate(eventId, request.getMemberId(), member);
+
+    return ResponseEntity.noContent().build();
+  }
+
   @GetMapping("/{id}/participants")
   public ResponseEntity<List<ParticipantResponse>> findParticipants(@PathVariable final Long id) {
     final List<ParticipantResponse> responses = eventService.findParticipants(id);

backend/emm-sale/src/main/java/com/emmsale/event/application/EventService.java

@@ -74,6 +74,21 @@ public Long participate(final Long eventId, final Long memberId, final Member me
     return participant.getId();
   }
 
+  public void cancelParticipate(final Long eventId, final Long memberId, final Member member) {
+    validateMemberNotAllowed(memberId, member);
+    if (!eventRepository.existsById(eventId)) {
+      throw new EventException(NOT_FOUND_EVENT);
+    }
+
+    participantRepository
+        .findByMemberIdAndEventId(memberId, eventId)
+        .ifPresentOrElse(
+            participant -> participantRepository.deleteById(participant.getId()),
+            () -> {
+              throw new EventException(EventExceptionType.NOT_FOUND_PARTICIPANT);
+            });
+  }
+
   @Transactional(readOnly = true)
   public List<EventResponse> findEvents(final EventType categoryName, final LocalDate nowDate,
       final Integer year, final Integer month,

backend/emm-sale/src/main/java/com/emmsale/event/domain/repository/ParticipantRepository.java

@@ -1,10 +1,12 @@
 package com.emmsale.event.domain.repository;
 
 import com.emmsale.event.domain.Participant;
+import java.util.Optional;
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.stereotype.Repository;
 
 @Repository
 public interface ParticipantRepository extends JpaRepository<Participant, Long> {
 
+  Optional<Participant> findByMemberIdAndEventId(final Long memberId, final Long eventId);
 }

backend/emm-sale/src/main/java/com/emmsale/event/exception/EventExceptionType.java

@@ -9,6 +9,7 @@ public enum EventExceptionType implements BaseExceptionType {
 
   NOT_FOUND_EVENT(HttpStatus.NOT_FOUND, "해당하는 행사를 찾을 수 없습니다."),
   FORBIDDEN_PARTICIPATE_EVENT(HttpStatus.FORBIDDEN, "참가하려는 사용자와 로그인된 사용자가 다릅니다."),
+  NOT_FOUND_PARTICIPANT(HttpStatus.NOT_FOUND, "해당 행사에 등록되지 않은 사용자입니다."),
   ALREADY_PARTICIPATED(HttpStatus.BAD_REQUEST, "이미 참가신청한 멤버입니다."),
   INVALID_STATUS(
       HttpStatus.BAD_REQUEST,

backend/emm-sale/src/main/resources/http/event.http

@@ -35,5 +35,14 @@ Authorization: bearer eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxIiwiaWF0IjoxNjkwMTk2OTY5L
   "memberId": 1
 }
 
+### Event 참여자 목록에서 멤버 삭제
+DELETE http://localhost:8080/events/1/participants
+Content-Type: application/json
+Authorization: bearer eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxIiwiaWF0IjoxNjkwMTk2OTY5LCJleHAiOjE2OTM3OTY5Njl9.yahaEBvKBA7xelNuykx8TROhemnzJAsu1Sv5rrSfCM0
+
+{
+  "memberId": 1
+}
+
 ### 행사 참여자 목록 조회
 GET http://localhost:8080/events/1/participants

backend/emm-sale/src/test/java/com/emmsale/event/api/EventApiTest.java

@@ -117,6 +117,28 @@ void participateEvent() throws Exception {
         .andDo(document("participate-event", requestFields));
   }
 
+  @Test
+  @DisplayName("Event에 사용자를 참여자 목록에서 제거할 수 있다.")
+  void cancelParticipateEvent() throws Exception {
+    //given
+    final Long eventId = 1L;
+    final Long memberId = 2L;
+    final EventParticipateRequest request = new EventParticipateRequest(memberId);
+    final String fakeAccessToken = "Bearer accessToken";
+
+    final RequestFieldsSnippet requestFields = requestFields(
+        fieldWithPath("memberId").type(JsonFieldType.NUMBER).description("멤버 식별자")
+    );
+
+    //when
+    mockMvc.perform(delete(format("/events/%s/participants", eventId))
+            .header("Authorization", fakeAccessToken)
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(request)))
+        .andExpect(status().isNoContent())
+        .andDo(document("participate-event-cancel", requestFields));
+  }
+
   @Test
   @DisplayName("특정 카테고리의 행사 목록을 조회할 수 있으면 200 OK를 반환한다.")
   void findEvents() throws Exception {