Cleanup authentication howto

[andypbarrett]

Description

This PR splits several how-to pages that demonstrate multiple methods into individual how-to documents.

The PR closes the following issues

#1383 , #1384 , #1386

"Ready for review" checklist

• Place this Pull Request (PR) in draft until it is ready for review (see below)
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Merge checklist

• PR title is descriptive
• PR body contains links to related and resolved issues (e.g. closes #1)
• If needed, CHANGELOG.md updated
• If needed, docs and/or README.md updated
• If needed, unit tests added (unsure how? see below!)
• All checks passing (tip: comment pre-commit.ci autofix if pre-commit is failing)
• At least one approval

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for you, via Continuous Integration (CI),
instead of running them locally. If anything fails and you're not sure why, just
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📚 Documentation preview 📚: https://earthaccess--1402.org.readthedocs.build/en/1402/

[github-actions]

👈 Launch a binder notebook on this branch for commit 1513030

I will automatically update this comment whenever this PR is modified