Fixed #36898 -- Documented SessionBase.is_empty().

[jafarkhan83]

Trac ticket number

ticket-36898

Branch description

To check whether the user has a session need to use Session.is_empty() but this method is not documented. Another way to check is request.session but that will always be populated if SessionMiddleware is enabled so it returns True on empty session too that makes it a pitfall.

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Checklist

• This PR follows the contribution guidelines.
• This PR does not disclose a security vulnerability (see vulnerability reporting).
• This PR targets the main branch.
• The commit message is written in past tense, mentions the ticket number, and ends with a period.
• I have checked the "Has patch" ticket flag in the Trac system.
• I have added or updated relevant tests.
• I have added or updated relevant docs, including release notes if applicable.
• I have attached screenshots in both light and dark modes for any UI changes.

[jacobtylerwalls]

Thanks @jafarkhan83, but next time please be more careful about following the commit message style referenced in the PR checklist. I'll update it for you.

[jacobtylerwalls]

@jafarkhan83 careful, there are multiple typos in your commit message, and no trailing period.