[FR] Add optional HTTP headers showing the source of the request when calling datasource

[uepoch]

Hello grafana !

On #17420 it is mentionned that backend_srv could be used to add tracking headers.

What would you like to be added:
We would like to generalize the use of X-Grafana-User / X-Grafana-Org-ID / X-Panel-ID / X-Dashboard-Id:

• Add them in all datasources, not just graphite / prometheus
• Send them from the frontend directly, so there's no need to use the datasource proxy (OPT)
• Replace X-Dashboard-ID by either the uid or the slug as it makes little sense to end-users

Why is this needed:
For a large company, with thousands of graphs, being able to identify traffic origin is a must-have, and it would really ease detection of unwanted behaviors to have theses informations directly provided by the Grafana calls.

[marefr]

Duplicate of #17410