1. Add the feature of using custom HTTP headers.
2. Customer wants to use custom HTTP headers when scraping application metrics. 
3. The customer requires this feature because each request for scrape metrics is stored in the trace server (Jaeger). The customer wants to configure those requests, the ones used for scraping metrics, and use specific headers to avoid generating traces on the server.
4. Prometheus, Prometheus-operator

There are two existing Pull Requests in progress for this change (this ticket is for tracking):

• https://github.com/prometheus-operator/prometheus-operator/pull/7000
• https://github.com/prometheus/prometheus/pull/14817