Pass custom headers to the search plugin

[pkukielka]

Problem description

With the uncommented configuration bellow it works (you need to paste valid token of course).

If I switch to X-Forwarded-User configuration (commented out) it fails with:

Access to fetch at 'https://piotr-kukielka.sgdev.dev/.api/graphql?SiteVersionAndCurrentUser' 
from origin 'http://piotr-kukielka.sgdev.dev' has been blocked by CORS policy: 
Request header field x-forwarded-user is not allowed by Access-Control-Allow-Headers in preflight response.

I suspect it might be due to http/https mismatch, see: #6919 (comment)
But If I try to keep https urls as they IMHO should be, it does not work with either config.

{
  "cody.override.serverEndpoint":  "https://piotr-kukielka.sgdev.dev",

  "cody.auth.externalProviders": [
    {
      "endpoint": "https://piotr-kukielka.sgdev.dev",
      "executable": {
        "commandLine": ["echo '{ \"headers\": { \"Authorization\": \"token sgp_local_YOUR_TOKEN\" } }'"],
        "shell": "/bin/bash"
      }
    },
//    {
//      "endpoint": "https://piotr-kukielka.sgdev.dev",
//      "executable": {
//        "commandLine": ["echo '{ \"headers\": { \"X-Forwarded-User\": \"SomeUser\" } }'"],
//        "shell": "/bin/bash"
//      }
//    }
  ]
}

Test plan

TBD

[pkukielka]

Changing https to http with .replace("https://", "http://") seems unnecessary or even buggy.
But with it and Authorization: token it works.

Without that replace, even with the Authorization: token configuration it fails with Failed to load Sourcegraph settings TypeError: Failed to fetch.

Btw. when trying to switch to https I changed line 18 as well, of course.
Interesting note: if I add both http and https scheme handler factories it fails as well, even if replace is in place...