Make git SHA and pipdeptree available as static files

[thekaveman]

Similar to e.g. benefits.calitp.org/static/sha.txt, it would be nice to be able to see the SHA of the deployed version of Eligibility Server as another quick check.

See also the work in cal-itp/benefits#1733 to get the Python dependency tree available as a static file in the image.

• Need to figure out how to serve static files from Eligibility Server -- ideally we aren't creating endpoints in the app, and this can be handled by nginx before the request even gets to the app (like how static files work in benefits).

[angela-tran]

From the Flask docs on static files, it is as simple as having a file in the /static directory.

I tested it out by creating a file at eligibility_server/static/sha.txt and launching the Flask app. I was able to see the file at <url>/static/sha.txt 🙂