No Merge Require - support prompt in authorize

[KevyVo]

There is not prompt field in the AuthorizationState by allowing this we are able to do the following.

The openauth package doesn't forward the prompt parameter from our app to GitHub. So when we tell it "hey, ask the user for consent again," it just ignores us and does a normal login.

We need two small plumbing changes inside openauth to pass prompt through:

1. issuer.ts — when our app sends /authorize?prompt=consent, the issuer needs to read it and forward it to the provider's
   internal /github/authorize?prompt=consent route
2. oauth2.ts — the provider needs to read it and put it on the actual GitHub URL:
   https://github.com/login/oauth/authorize?...&prompt=consent

Without both, the prompt=consent gets dropped along the way and GitHub never sees it.

This PR will solve this. There was PR in portal related to this: https://github.com/DefangLabs/portal/pull/484.

There no need to merge this PR unless we want to sync the Git subtree.