When using the authorize-project plugin to run jobs with a specific user, then credentials are not retrieved correctly, only anonymous: is used for basic auth.

How to reproduce

1. Create a global "Username with password" credential with id example-id.
2. Setup a pipeline with a Jenkinsfile as follows.

node {
  artifactoryDownload(
    server: Artifactory.newServer(url: 'http://...', credentialsId: 'example-id'),
    spec: '{ "files": [{"pattern": "example" }] }',
  )
}

3. Under "Manage Jenkins / Configure Global Security" enable security.
4. Configure a user that is granted all permissions.
5. Under "Manage Jenkins / Configure Global Security / Access Control for Builds" configure "Project default Build Authorization" to use this user.
6. Perform a build.

On the server side the Authorization header contains Basic YW5vbnltb3VzOg== which decodes to anonymous:.