Improve the CI

[jonathan-s]

Feature Request

Describe the solution you'd like

Improve github actions

• Lint the code.
• Run functional tests. See Tests with passwords are mocked out -> docker containers #360
• Run tests for djongo
• Include coveralls / coverage after last success.
• Set up action for when pushing a tag. Should be some kind of release. See Add machinery for auto-releases #326

PR link

See #368 where we remove travis and replace it with github actions.