Feature request: Add log to debug interaction with GitLab

The instructions in the plugin say to "Link to an existing entity file
Example: https://github.com/backstage/backstage/blob/master/catalog-info.yaml"

That URL produces the file in the UI (though not the raw version), but putting that in the Backstage UI produces a 400 from (presumably GitLab?)

There's nothing in the frontend or backend log that indicates what URL it tried to use, or how GitLab responded.

Maybe also the backend should be able to handle repositories URLs (/api/v4/projects/:id/repository/files/:filepath/raw?ref=branch) also. That URL would work, but the Backstage UI complains that it's not a file (I'm guessing because it doesn't end in .yaml).

Basically I have no way to write a URL that gets catalog-info.yaml that will be accepted by both the Backstage UI and the GitLab UI via a personal access token. And I'm kind of in the dark about where the problem is, because Backstage doesn't say what it's trying to do.

Trying the sort of URL recommended by the UI produces this:

Not too surprising, since this is what curl does:

$ curl -D - -H "PRIVATE-TOKEN: $GITLAB_TOKEN" 'https://gitlab.be-md.ncbi.nlm.nih.gov/..../project-slug/blob/backstage/catalog-info.yaml'
HTTP/1.1 302 Found
Server: nginx
Date: Tue, 22 Nov 2022 22:40:10 GMT
Content-Type: text/html; charset=utf-8
Location: https://gitlab.be-md.ncbi.nlm.nih.gov/users/sign_in
X-Download-Options: noopen
X-Frame-Options: SAMEORIGIN
X-Permitted-Cross-Domain-Policies: none
X-Request-Id: 01GJGQZBB26P8YTM672X3PV9MT
X-Runtime: 0.037568
X-Ua-Compatible: IE=edge
X-Xss-Protection: 1; mode=block
Strict-Transport-Security: max-age=63072000
Referrer-Policy: strict-origin-when-cross-origin

(Some headers redacted)