Iss-10: Add Unit Test Architecture for the Back-End

[klondikemarlen]

Fixes https://github.com/elthran/UDK/issues/10

Basic test environment.

Requires: docker-compose down -v && docker-compose build && ./bin/dev test the first time. After that ./bin/dev test is find.

Uses

• https://docs.pytest.org/en/stable/
• https://expects.readthedocs.io/en/stable/matchers.htm