CORS: Leave user configure CORS in prometheus.yml

[aloababa]

According to prometheus code Allowed Origin is always set to '*'.

var corsHeaders = map[string]string{ "Access-Control-Allow-Headers": "Accept, Authorization, Content-Type, Origin", "Access-Control-Allow-Methods": "GET, OPTIONS", "Access-Control-Allow-Origin": "*", "Access-Control-Expose-Headers": "Date", }

So what if i want a single allowed origin ?

It would be nice to allow user configure allowed origins or disable cors in prometheus.yml

[brian-brazil]

Per previous discussions, this would make more sense as a flag.

[geekodour]

I'll try to send a PR for this one today.

[cstyan]

looks like the two PR's fix this, can we close?