Perses does not propagate proxy headers to all api calls

[th3M1ke]

Problem

For some reason, perses does not propagate headers for the next endpoints:

• /api/v1/label/name/values
• /api/v1/metadata
• /api/v1/series
  on a pages "Add panel" and "Explore"

STR:

1. go to https://demo.perses.dev/projects/mike/dashboards/mike_dashboard?var-job=alertmanager&start=1h&refresh=0s
2. edit the existing panel or add a new one
3. type something in PromQL Expression input
4. Check header for any of described above endpoints

Current result

proxy headers do not propagated into the request headers

Expected result

proxy header should be propagate to all API calls