Merging into one branch causes all environments to restart

[angela-tran]

The expected behavior is for only the environment corresponding to the branch to restart.

See Slack discussions:

• https://cal-itp.slack.com/archives/C022HHSEE3F/p1704916040354209?thread_ts=1704914522.128459&cid=C022HHSEE3F
• https://cal-itp.slack.com/archives/C022HHSEE3F/p1707344329873899

We want to avoid restarting the app when it's not necessary, since it can sometimes cause a little bit of downtime.

[angela-tran]

This is from the Slack thread, but gonna put here too:

Maybe it would be better to have the deploy GitHub workflow tell Azure to restart the specific app service
This section has somewhat of an example: https://learn.microsoft.com/en-us/azure/app-service/app-service-sql-github-actions#build-push-and-deploy-your-image

[angela-tran]

Looked briefly into what we'd need to use the Azure Login action, but I don't have access to Microsoft Entra ID in the CDT directory so currently cannot make any progress on that

[thekaveman]

I think we can use the azure/webapps-deploy action step with a Publish Profile per environment, avoiding the need to authenticate with a service principal and getting involved with Microsoft Entra ID.

Plan so far

dev

• Turn off webhook deploys (e.g. the Container Registry option) in the Azure App Service "Deployment Center"; instead choose the GitHub Actions option
• Fill in details for GitHub Actions deploy; don't generate a workflow file, we'll use the existing one
  
• Create an environment variable to hold the name of the Azure App Service, AS-CDT-PUB-VIP-CALITP-D-001
• Create an environment secret to hold the contents of the Publish Profile for this App Service
• Add a step in the deploy workflow that uses azure/webapps-deploy with the above config
• Deactivate the webhooks for dev, test, and prod

See #2111 for post-merge follow-up steps.