add check if the app exists in DB before creating it

cliapp/cliapp/cli.py

@@ -57,8 +57,14 @@ def create_app(slug, name):
     obj.name = name
     obj.slug = slug
 
-    db.session.add(obj)
-    db.session.commit()
+    app = db.session.query(App).filter_by(slug=slug).first()
+
+    if app is not None:
+        db.session.add(obj)
+        db.session.commit()
+    else:
+        current_app.logger.info(f"App definition: {name} ({slug}) already exists in database")
+
 
 
 @app_cli.command("list")