Revert "Remove tenant_header_key from config (#2414)"

[joe-elliott]

Reverts #2414. This config field was in use by RH for authentication through jaeger-query.

[github-actions]

Hello @joe-elliott!
Backport pull requests need to be either:

• Pull requests which address bugs,
• Urgent fixes which need product approval, in order to get merged,
• Docs changes.

Please, if the current pull request addresses a bug fix, label it with the type/bug label.
If it already has the product approval, please add the product-approved label. For docs changes, please add the type/docs label.
If the pull request modifies CI behaviour, please add the type/ci label.
If none of the above applies, please consider removing the backport label and target the next major/minor release.
Thanks!

[github-actions]

The backport to release-v2.2 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-2795-to-release-v2.2 origin/release-v2.2
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x d9210d04c6782c155b537299b9f7923506fe0f95
# When the conflicts are resolved, stage and commit the changes
git add . && git cherry-pick --continue

If you have the GitHub CLI installed:

# Create the PR body template
PR_BODY=$(gh pr view 2795 --json body --template 'Backport d9210d04c6782c155b537299b9f7923506fe0f95 from #2795{{ "\n\n---\n\n" }}{{ index . "body" }}')
# Push the branch to GitHub and a PR
echo "${PR_BODY}" | gh pr create --title "[release-v2.2] Revert \"Remove tenant_header_key from config (#2414)\"" --body-file - --label "type/bug" --label "backport" --base release-v2.2 --milestone release-v2.2 --web

Or, if you don't have the GitHub CLI installed (we recommend you install it!):

# If you don't have the GitHub CLI installed: Push the branch to GitHub and manually create a PR:
git push --set-upstream origin backport-2795-to-release-v2.2
# Remove the local backport branch
git switch main
git branch -D backport-2795-to-release-v2.2

Unless you've used the GitHub CLI above, now create a pull request where the base branch is release-v2.2 and the compare/head branch is backport-2795-to-release-v2.2.