[BUG] Populate user_guide/authentication

[andypbarrett]

Is this issue already tracked somewhere, or is this a new report?

• [X] I've reviewed existing issues and couldn't find a duplicate for this problem.

Current Behavior

User Guide Authentication page needs populating

Expected Behavior

Contains complete documentation with examples for authenticating using earthaccess

Steps To Reproduce

See https://earthaccess.readthedocs.io/en/latest/user_guide/authenticate/

Environment

- OS:
- Python:

Additional Context

No response

[andypbarrett]

Methods to document as defined in Auth

• login
  • strategy
  • persist
  • system
• get_s3_credentials
• get_fsspec_https_session - this maybe better in access
• get_requests_https_session - this maybe better in access
• get_edl_token