[tests,dependencies] install and configure coverage reports

The reports will be printed on the terminal and written in xml.

A new just recipe is added as well: `just cov`

closes: #9

.woodpecker/workflow.yaml

@@ -23,7 +23,7 @@ steps:
       - python -m venv venv
       - . venv/bin/activate
       - python -m pip install --disable-pip-version-check --no-input --quiet -r requirements/test.txt
-      - python -m pytest
+      - python -m pytest --cov --cov-report term
 
 services:
   - name: database