Issue/3 test back end

.gitlab/server.gitlab-ci.yml

+image: python
+
+cache:
+  paths:
+    - server/env/
+
+before_script:
+  - python --version
+  - pip install virtualenv
+  - cd server/
+  - python -m venv env
+  - source env/bin/activate
+  - pip install -r requirements.txt
+
+test-server:
+  stage: test
+  script:
+    - pytest --cov app tests/