Transfers: metrics API endpoint, allow to group RSEs by attribute in response

[rdimaio]

Usage: requests/metrics?group_response_by=[attr]

Note: I didn't test this as I am not yet sure how to test API requests. I would appreciate some guidance on this if possible.

Fix #6564

[dchristidis]

I’m concerned that the name group_response_by and the documentation around it can be misleading or not intuitive. I would be more precise that this is about RSE attributes.

Also, links should not be silently omitted if the RSE attribute does not exist (maybe use something like rse.attributes.get(key, 'UNKNOWN') instead ?)

[rdimaio]

I’m concerned that the name group_response_by and the documentation around it can be misleading or not intuitive. I would be more precise that this is about RSE attributes.

Also, links should not be silently omitted if the RSE attribute does not exist (maybe use something like rse.attributes.get(key, 'UNKNOWN') instead ?)

@dchristidis thanks for the comments. Would group_response_by_rse_attribute be an acceptable name or do you have other suggestions?

[dchristidis]

The presence of ‘response’ feels unnecessary. Maybe group_by_attribute or group_by_rse_attribute?

[rdimaio]

Please ignore the changes in test_request.py that I accidentally added in the first force-push; I reverted them in the second force-push