Add clarification about auth parameter in ClientSession

[MaximZemskov]

What do these changes do?

These changes clarify the behavior of the auth parameter in ClientSession.

Are there changes in behavior for the user?

No.

Is it a substantial burden for the maintainers to support this?

No.

Related issue number

#6764

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
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• Add a new news fragment into the CHANGES/ folder

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  • if you don't have an issue number, change it to the pull request
    number after creating the PR

    • .bugfix: A bug fix for something the maintainers deemed an
      improper undesired behavior that got corrected to match
      pre-agreed expectations.
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    • .deprecation: A declaration of future API removals and breaking
      changes in behavior.
    • .breaking: When something public is removed in a breaking way.
      Could be deprecated in an earlier release.
    • .doc: Notable updates to the documentation structure or build
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    • .contrib: Stuff that affects the contributor experience. e.g.
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    • .misc: Changes that are hard to assign to any of the above
      categories.

  • Make sure to use full sentences with correct case and punctuation,
    for example:

    Fixed issue with non-ascii contents in doctest text files
    -- by :user:`contributor-gh-handle`.

    Use the past tense or the present tense a non-imperative mood,
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.27%. Comparing base (1d170d3) to head (7cef2bf).
Report is 1071 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #8953   +/-   ##
=======================================
  Coverage   98.27%   98.27%           
=======================================
  Files         107      107           
  Lines       34226    34226           
  Branches     4058     4058           
=======================================
  Hits        33637    33637           
  Misses        416      416           
  Partials      173      173           

Flag	Coverage Δ
CI-GHA	98.17% <ø> (ø)
OS-Linux	97.83% <ø> (ø)
OS-Windows	96.24% <ø> (ø)
OS-macOS	97.51% <ø> (-0.01%)	⬇️
Py-3.10.11	97.60% <ø> (ø)
Py-3.10.14	97.53% <ø> (ø)
Py-3.11.9	97.77% <ø> (ø)
Py-3.12.5	97.88% <ø> (ø)
Py-3.9.13	97.49% <ø> (ø)
Py-3.9.19	97.43% <ø> (ø)
Py-pypy7.3.16	97.04% <ø> (ø)
VM-macos	97.51% <ø> (-0.01%)	⬇️
VM-ubuntu	97.83% <ø> (ø)
VM-windows	96.24% <ø> (ø)

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[Dreamsorcerer]

I was thinking about this last night, and maybe one case we should restrict it to an origin would be when base_url is in use.
Might be worth looking at if you'd like to make another contribution?

[patchback]

Backport to 3.10: 💚 backport PR created

✅ Backport PR branch: patchback/backports/3.10/51ea3b39a454993dcea4bb9d3d3baa4f1a515eb0/pr-8953

Backported as #8954

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[patchback]

Backport to 3.11: 💚 backport PR created

✅ Backport PR branch: patchback/backports/3.11/51ea3b39a454993dcea4bb9d3d3baa4f1a515eb0/pr-8953

Backported as #8955

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[MaximZemskov]

@Dreamsorcerer I think that's a good idea. I'll make a PR either today or tomorrow.