Update How Tos about request id

[enadeau]

I change the function name for the request_id example as the name implies the header is only added on error response while it's added to every response.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (1665cab) to head (2b8cc3c).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #1010   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           51        51           
  Lines         2228      2228           
  Branches        35        35           
=========================================
  Hits          2228      2228           

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