Fix LegacyAPIWarning of SQLalchemy

server/src/util/generic_relationships.py

@@ -1,3 +1,4 @@
+from extensions import db
 from models.area import Area
 from models.crag import Crag
 from models.line import Line
@@ -10,15 +11,15 @@ def check_object_exists(object_type, object_id):
     Check if an object with the given object_type and object_id exists.
     """
     if object_type == "User":
-        return User.query.get(object_id) is not None
+        return db.session.get(User, object_id) is not None
     if object_type == "Line":
-        return Line.query.get(object_id) is not None
+        return db.session.get(Line, object_id) is not None
     if object_type == "Area":
-        return Area.query.get(object_id) is not None
+        return db.session.get(Area, object_id) is not None
     if object_type == "Sector":
-        return Sector.query.get(object_id) is not None
+        return db.session.get(Sector, object_id) is not None
     if object_type == "Crag":
-        return Crag.query.get(object_id) is not None
+        return db.session.get(Crag, object_id) is not None
     return False