Resolve auth for Git providers that use tokens

[tcrespog]

Those Git providers that rely on tokens for authentication (GitLab, Gitea, Bitbucket) do not need username and password to be defined too.

This PR tweaks the logic that determines whether a Git provider has authentication properties configured or not to take into account the sole presence of the token field.

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[pditommaso]

It may be better to override it in the class that has support for it. I only see it supported by these

nextflow/modules/nextflow/src/main/groovy/nextflow/scm/GiteaRepositoryProvider.groovy

Lines 45 to 55 in b334df1

	@Override
	protected String[] getAuth() {
	if( config.token ) {
	// set the token in the request header
	// https://docs.gitea.io/en-us/api-usage/#authentication
	return new String[] { "Authorization", "token $config.token" as String }
	}
	else {
	return EMPTY_ARRAY
	}
	}

nextflow/modules/nextflow/src/main/groovy/nextflow/scm/GitlabRepositoryProvider.groovy

Lines 42 to 51 in b334df1

	protected String[] getAuth() {
	if( config.token ) {
	// set the token in the request header
	return new String[] { "PRIVATE-TOKEN", config.token }
	}
	if( config.password ) {
	return new String[] { "PRIVATE-TOKEN", config.password }
	}
	return EMPTY_ARRAY
	}

[tcrespog]

It may be better to override it in the class that has support for it. I only see it supported by these

The idea of adding it in the parent class is that more may come, such as #6209.