[BUG] Self Hosted Token authentication

[paulwilljones]

Describe the bug When using a self hosted registry, credentials are provided which are used to retrieve a token. If the registry does not implement a token service, the endpoint returns a 404 and version-checker cannot authenticate to the registry.

$ k plogs -n version-checker -p version-checker-7db59c4996-8hj99 -c version-checker
...
error: failed to setup image registry clients: failed to create selfhosted client "http://docker-registry.registry.svc.cluster.local:5000": failed to setup token auth (404): 404 page not found

$ curl -i http://XXXXXX:XXXXXX@localhost:30000/v2/_catalog
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Docker-Distribution-Api-Version: registry/2.0
X-Content-Type-Options: nosniff
Date: Thu, 29 Aug 2024 08:32:30 GMT
Content-Length: 37

{"repositories":["my-app"]}

$ curl -i http://XXXXXX:XXXXXX@localhost:30000/v2/token
HTTP/1.1 404 Not Found
Content-Type: text/plain; charset=utf-8
Docker-Distribution-Api-Version: registry/2.0
X-Content-Type-Options: nosniff
Date: Thu, 29 Aug 2024 08:33:26 GMT
Content-Length: 19

404 page not found

This could be an edge case, and there should be a token endpoint in which case a 404 is the right response and basic auth shouldn't be used.

To Reproduce Steps to reproduce the behavior:

1. Deploy registry to kind
2. Deploy version-checker with selfhosted values:

   ...
   selfhosted:
   - name: registry
   host: http://docker-registry.registry.svc.cluster.local:5000
   username: XXXXXX
   password: XXXXXX

3. Push an image into registry using kaniko
4. Create docker-registry secret and deploy image from local registry

   apiVersion: v1
   kind: Pod
   metadata:
   annotations:
   enable.version-checker.io/test: "true"
   name: image-from-reg
   ...
   spec:
   containers:
   - image: docker-registry.registry.svc.cluster.local:5000/my-app:0.0.1
   ...

   Expected behavior Basic auth should be used when token endpoint returns 404 so version-checker can authenticate with the registry.

Environment (please complete the following information):

• Version-Checker: 0.7.0
• kind 0.23.0
• registry 2.8.1