[proxy] Pre-flight server authentication related endpoints to add additional latency

[andrew-farries]

Description

Pre-flight requests to server /auth/* endpoints in order to decide whether to send the actual request to server or slow-server depending on the value of the slow_database feature flag.

This change will affect requests to following paths on server: /auth/github/callback /auth /auth/* /apps /apps/*

The pre-flight approach taken here is the same as we use for other api/* endpoints (#14897) and websocket connections (#15035).

Related Issue(s)

Part of #9198 and #14965

How to test

1. Open the preview environment and start a workspace.
2. Take the instance id of the running workspace from the application db.
3. Hit https://af-add-lat37f4cc0217.preview.gitpod-dev.com/api/auth/workspace-cookie/your-instance-id
4. Enable the slow_database feature flag for your user id in the preview.
5. Wait up to 3 minutes for the configcat client to fetch the updated feature flag.
6. Hit https://af-add-lat37f4cc0217.preview.gitpod-dev.com/api/auth/workspace-cookie/your-instance-id and observe that the endpoint now has additional latency.

Release Notes

NONE

Documentation

Werft options:

• /werft with-local-preview
  If enabled this will build install/preview
• /werft with-preview
• /werft with-slow-database
• /werft with-large-vm
• /werft with-integration-tests=all
  Valid options are all, workspace, webapp, ide, jetbrains, vscode, ssh

[werft-gitpod-dev-com]

started the job as gitpod-build-af-add-latency-to-auth-endpoints.8 because the annotations in the pull request description changed
(with .werft/ from main)