redirectURI without the domain?

Right now I have to do this:

return new GitHubStrategy(
	{
		clientId: process.env.GITHUB_CLIENT_ID,
		clientSecret: process.env.GITHUB_CLIENT_SECRET,
		redirectURI: 'https://www.epicstack.dev/auth/github/callback',
	},
	async () => {
		// ...
	}
)

But I want to be able to do this:

return new GitHubStrategy(
	{
		clientId: process.env.GITHUB_CLIENT_ID,
		clientSecret: process.env.GITHUB_CLIENT_SECRET,
		redirectURI: '/auth/github/callback',
	},
	async () => {
		// ...
	}
)

And then the strategy would get the domain from the request.

This would make it so we can run this locally and on staging. Additionally with this improvement people wouldn't have to change this hard-coded URL when creating an epic app.

Start at the GitHubStrategy entry point and trace how redirectURI is used when handling the request and constructing the OAuth callback URL. Confirm that a path-only redirectURI can use the request domain while preserving the existing absolute-URL behavior; no specific files or tests are named in the issue.