This PR changes the following behavior.

• 1. Set coder.image.pullPolicy=Always (otherwise, we always deploy the image from the first deployment of the PR)
• 2. Use the Helm chart from the current branch (we can test the Helm chart, too, @ericpaulsen )
• 3. Comment deployment link on the last comment
• 4. Comment deployment URL.
• 5. Remove serviceAccount.enableDeployments=true as this is the default
• 6. Enable GitHub OAuth
• 7. Automatically create the first user (I guess it's not needed if we have GitHub OAuth and allow signups)
• 8. Test everything works (the most difficult part)
• 9. Add a script to deploy a PR from CLI (e.g.) (./scripts/deploy-pr.sh)
• 10. Allows skipping build the image with --skip-build flag

cc: @bpmct