MAPG-235 new challenge can be created and is prepared

src/Repository/UserInChallengeRepository.php

@@ -31,4 +31,13 @@ class UserInChallengeRepository
 
         yield from $this->pdm->selectMultipleFromDb($select, UserInChallenge::class);
     }
+
+    public function isUserParticipatingInChallenge(int $userId, Challenge $challenge): bool
+    {
+        $select = new Select(\Container::$dbConnection, 'user_in_challenge');
+        $select->where('user_id', '=', $userId);
+        $select->where('challenge_id', '=', $challenge->getId());
+
+        return $select->count();
+    }
 }