PMT-15: Added a deleteProject by ID method

src/main/java/de/hmmh/pmt/ApiController.java

@@ -35,6 +35,16 @@ public class ApiController implements DefaultApi {
         return Optional.empty();
     }
 
+    @Override
+    public ResponseEntity<Void> deleteProject(Long id) {
+        if (!projectRepository.existsById(id)) {
+            return ResponseEntity.notFound().build();
+        }
+
+        projectRepository.deleteById(id);
+        return ResponseEntity.noContent().build();
+    }
+
     @Override
     public ResponseEntity<GetAllProjectsDTO> getAllProjects() {
         GetAllProjectsDTO response = new GetAllProjectsDTO();