fix(basic-auth): add missing www-authenticate headers

[nowNick]

Summary

When kong returns 401 Unauthorized response it should return WWW-Authenticate header with proper challenge. Basic auth was missing this header on some responses. Previously it only returned this header when Authorization or Proxy-Authorization was missing but the RFC states that it should return it for every 401 response. This PR also adds a possibility to configure a parameter - realm (defaults to service).

Related PRs:

• fix(hmac): add missing www-authenticate headers #11791
• fix(jwt): add missing www-authenticate headers #11792
• fix(key-auth): add missing www-authenticate headers #11794
• fix(ldap): add missing www-authenticate headers #11820
• fix(oauth2): add missing www-authenticate headers #11833

RFCs & Materials

• https://httpwg.org/specs/rfc7235.html#status.401
• https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/WWW-Authenticate

Checklist

• The Pull Request has tests
• A changelog file has been created under changelog/unreleased/kong or skip-changelog label added on PR if changelog is unnecessary. README.md
• N/A There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com - PUT DOCS PR HERE

Full changelog

• add WWW-Authenticate header to all basic-auth 401 response

Issue reference

• Fix WWW-Authenticate header not present when Kong and plugins return HTTP status 401 #7772
• KAG-321

[kikito]

Approved with a small comment

[locao]

@nowNick there are conflicts in this PR, can you check please?

[team-gateway-bot]

Cherry-pick failed for master, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git remote add upstream https://github.com/kong/kong-ee
git fetch upstream master
git worktree add -d .worktree/cherry-pick-11795-to-master-to-upstream upstream/master
cd .worktree/cherry-pick-11795-to-master-to-upstream
git checkout -b cherry-pick-11795-to-master-to-upstream
ancref=$(git merge-base 15d6f4cec8f6253ff73f157cb37d1a2cdce8cb94 54bdfb8494166ff357f55486b15e3965101597b6)
git cherry-pick -x $ancref..54bdfb8494166ff357f55486b15e3965101597b6