Resolve "Create missing service classes"

Closes #16 (closed)

src/main/java/cz/muni/ics/kypo/training/adaptive/repository/phases/AbstractPhaseRepository.java

@@ -54,4 +54,6 @@ public interface AbstractPhaseRepository extends JpaRepository<AbstractPhase, Lo
                     "WHERE ap.id = :phaseId")
     Optional<AbstractPhase> findByIdWithDefinition(@Param("phaseId") Long phaseId);
 
+    @Query("SELECT ap FROM AbstractPhase ap WHERE ap.trainingDefinition.id = :trainingDefinitionId AND ap.order = 0")
+    Optional<AbstractPhase> findFirstPhaseOfTrainingDefinition(@Param("trainingDefinitionId") Long trainingDefinitionId);
 }