Improve error message for invalid JWT Header values (backport #7121)

[IvanGoncharov]

Enhanced parsing error messages for JWT Authorization header values now provide developers with clear, actionable feedback while ensuring that no sensitive data is exposed.

Examples of the updated error messages:

-         Header Value: '<invalid value>' is not correctly formatted. prefix should be 'Bearer'
+         Value of 'authorization' JWT header should be prefixed with 'Bearer'

-         Header Value: 'Bearer' is not correctly formatted. Missing JWT
+         Value of 'authorization' JWT header has only 'Bearer' prefix but no JWT token

Fixes #issue_number

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Checklist

Complete the checklist (and note appropriate exceptions) before the PR is marked ready-for-review.

• Changes are compatible¹
• Documentation² completed
• Performance impact assessed and acceptable
• Tests added and passing³
  • Unit Tests
  • Integration Tests
  • Manual Tests

Exceptions

Note any exceptions here

Notes

[ROUTER-1212]: https://apollographql.atlassian.net/browse/ROUTER-1212?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

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This is an automatic backport of pull request #7121 done by Mergify.

Footnotes

1. It may be appropriate to bring upcoming changes to the attention of other (impacted) groups. Please endeavour to do this before seeking PR approval. The mechanism for doing this will vary considerably, so use your judgement as to how and when to do this. ↩

2. Configuration is an important part of many changes. Where applicable please try to document configuration examples. ↩

3. Tick whichever testing boxes are applicable. If you are adding Manual Tests, please document the manual testing (extensively) in the Exceptions. ↩

[mergify]

Cherry-pick of 65c20a8 has failed:

On branch mergify/bp/1.x/pr-7121
Your branch is up to date with 'origin/1.x'.

You are currently cherry-picking commit 65c20a8b.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   .changesets/fix_improve_jwt_errors.md
	modified:   apollo-router/src/plugins/authentication/tests.rs

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   apollo-router/src/plugins/authentication/error.rs
	both modified:   apollo-router/src/plugins/authentication/jwks.rs

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[svc-apollo-docs]

✅ Docs preview has no changes

The preview was not built because there were no changes.

Build ID: 29bde918b04bbb1a71d1efd8