Consistently add outcome tag to all HTTP client instrumentation #3729
Description
To enhance metrics filtering, a grouping outcome tag would be helpful in http_client_requests, similar to the outcome tag in the http_server_requests.
For less matured metrics systems (like CloudWatch) it's impossible to filter by patterns, and having a similar grouping in HTTP client and server metrics would be very helpful.
PS. I couldn't find any issue related to this one, so I created a new one. Please let me know if I've overlooked something
PS2. If such a tag makes sense, I'm happy to raise a PR and work on that.