Fix #216731 "Fetching author API under relative url"

What does this MR do?

issue #216731 (closed)

I added relative_url prefix to Generated API URL.

This fix affects the author filter when entering it on the commits page.

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• Changelog entry
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• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
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Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

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Closes #216731 (closed)