Unit tests only run in Docker on Github

[medley56]

The tests currently require secrets that are only available in a Github context and passed into the Docker container. This makes it impossible to test the library locally.

I suggest we mock out whatever API is being called with these secrets (Space Track?) and modify the tests so they can be run locally, ideally with or without Docker. Dockerized tests are extremely consistent and helpful for CI, but it's useful for development if the tests can also be run without requiring Docker.