Merge branch 'dev' into feature/17-automated_tests

# Conflicts:
#	src/app.ts
#	src/controllers/RunnerController.ts
#	src/controllers/RunnerOrganisationController.ts
#	src/controllers/RunnerTeamController.ts
#	src/models/actions/CreateParticipant.ts

src/models/actions/CreateParticipant.ts

@@ -17,7 +17,7 @@ export abstract class CreateParticipant {
      * Optional.
      */
     @IsString()
-    @IsNotEmpty()
+    @IsOptional()
     middlename?: string;
 
     /**