Add CI check for missing migrations

.gitlab-ci.yml

@@ -43,6 +43,16 @@ backend-lint:
   script:
     - flake8
 
+backend-migrations:
+  stage: test
+
+  services:
+    - postgres:latest
+
+  script:
+    - pip install -e .
+    - arkindex/manage.py makemigrations --check --noinput --dry-run -v 3
+
 backend-openapi:
   stage: build