The flows are crucial to the extension and I wanted to be able to declare which can be used when in a declarative way. This reworks the flows into that model.
Additionally, it pulls in the Client ID and secret from a config which will allow us to not rely on the vscode.dev proxy on Desktop (because we can make a distro change that includes the secret... which isn't a real secret, says GitHub)... unfortunately we still need to rely on it for Web due to CORS but we're in a position where it will be easy to rip the proxy out when GH supports it.
* Improve GHES flow
It's clear to me now that a lot of users of the GHES flow have auth behind a VPN. Something that we cannot support in the OAuth flow because we require making a request to vscode.dev who makes a request to the GHES instance.
In light of this, we will remove the OAuth flow for GHES. Fear not, though... because both the Device Code Flow and the PAT flow are there and the PAT flow has been improved in 1.75... so in conclusion, I think GHES is handled as best we can with this PR.
Additionally, there is some "Hosted GitHub Enterprise" scenarios popping up, and this future proofs that by allowing "Hosted GitHub Enterprise" experiences to go through the OAuth flow because we know for a fact that they will be accessible from vscode.dev.
Fixes#169619
Fixes https://github.com/microsoft/vscode-internalbacklog/issues/3398
* Use api. sub domain and update telemetry logic
