This PR adds a few helpful additions regarding authentication.
Changes:
* e2e tests are now run on test_oauth via a passed config.yaml
* node dev server correctly handles `/login` and `/logout` endpoints to make developing for auth easier
* Introduced auth e2e tests to check that buttons display and work
* Collect all env vars in one, easy-to-find place
Past state:
* Default environement variables were stored in both client/package.json
and client/__tests__/e2e/config.js
* Constants that should have been linked--like the cellxgene server port
during testing--were repeated.
With this commit:
* All environment variables are parameterized
* All environment variables are packaged in default env files
* Move npm scripts to client Makefile
* Respond to feedback from @seve and @bkmartinjr