Fix division and group import inconsistencies

After group import:

• Either
  • Every member is in the same division
  • The group also belongs to that division
• Or
  • The group and members have no division

After division import:

• Every group any of the people imported is in will be in the same division
• All members of those groups will be in the same division

src/main/java/nl/tudelft/labracore/repository/StudentGroupRepository.java

@@ -21,10 +21,12 @@ import static com.querydsl.jpa.JPAExpressions.select;
 import static nl.tudelft.labracore.model.QRole.role;
 import static nl.tudelft.labracore.model.QStudentGroup.studentGroup;
 
+import java.util.Collection;
 import java.util.List;
 
 import nl.tudelft.labracore.model.Module;
 import nl.tudelft.labracore.model.ModuleDivision;
+import nl.tudelft.labracore.model.Person;
 import nl.tudelft.labracore.model.StudentGroup;
 
 import org.springframework.data.jpa.repository.JpaRepository;
@@ -118,6 +120,17 @@ public interface StudentGroupRepository
 						"StudentGroup was not found for person, module: " + personId + ", " + moduleId));
 	}
 
+	/**
+	 * @param  moduleId The id of the module to lookup.
+	 * @param  people   The people to look for
+	 * @return          The groups that contains the given people in the given module.
+	 */
+	default List<StudentGroup> findAllByModuleAndPersonIn(Long moduleId, Collection<Person> people) {
+		BooleanExpression q = studentGroup.module.id.eq(moduleId).and(
+				studentGroup.members.any().person.in(people));
+		return findAll(q);
+	}
+
 	/**
 	 * @param  personId     The id of the person to lookup.
 	 * @param  assignmentId The id of the assignment to lookup.