As a user I would like to see an example how to open GitHub app consent dialog to obtain access token.

The purpose for this issue is to enable a workflow to authenticate against GitHub OAuth App using user's credentials.

Once the user is authenticated, then the orchestrator backend plugin will send the consent token retrieved from the GitHub OAuth App to the workflow's execution call as a header parameter.

In the example we'd like to offer the user to select from any of the configured GitHub provider, however, need to verify this isn't limited only to the provider the user used to login and that this behavior complies with Backstage.

Based on the selection, the user will get a popup to authorize the workflow to access GitHub using its token.

An example of the use case can be found here:

https://github.com/ricardozanini/poc-sonataflow-gh-oauth

More info can be find here: https://docs.github.com/en/apps/creating-github-apps/authenticating-with-a-github-app