User authentication

[JWCook]

Reminder to research options for user authentication.

Besides possible future features like observation upload/bidirectional sync, authentication would be needed for a few useful pieces of info:

• private/obscured coordinates
• photo original filename

However, using the user credentials flow (the only one currently supported in pyinaturalist), creating an OAuth application is a pretty big hurdle for most users. The Authorization Code + PKCE flow would probably be the best option, but quite a bit of implementation effort: pyinat/pyinaturalist#692

Reference:

• https://www.inaturalist.org/pages/api+reference#auth
• https://pyinaturalist.readthedocs.io/en/stable/user_guide/authentication.html