Pass the QA User-Agent header to the CustomersDot HTTP client
What does this MR do and why?
Pass the QA User-Agent
header (if provided) to the CustomersDot HTTP client.
The CustomersDot portal has configured requests rate limiting. Because of that
some of our E2E tests fail and to resolve them we need to pass the User-Agent
header
with a special value to bypass the rate limiting.
Closes #454579