Preserve host header even with extra trusted root certificates

[chrismilson]

Checklist

• [ ] The title of the PR is clear and informative
• [ ] If applicable, the changes made in the PR have proper test coverage
• [ ] Issues addressed by the PR are mentioned in the description followed by Fixes.

Description

• Add a new boolean annotation /override-backend-hostname;
• When defined, determines whether the backend host header should be overwritten or not;
• When undefined, falls back to original behaviour of using the value of Trusted Root Certificates.

Fixes

#1520

[chrismilson]

@microsoft-github-policy-service agree

[chrismilson]

Not sure how to get the Merge Builds check to succeed - error message is pretty non-descriptive.

[chrismilson]

@akshaysngupta @alxyzc Could I please get a review?