Deployer - Return preferred / default URL (particularly host) for deployed app

[huntharo]

Motivations

• The deployer service should know what it's primary URL is
• Callers can have a difficult time figuring out what URL maps to the deployer that they deployed their app to

Acceptance Criteria

• Add a CLI command to get/set the primary root URL used by the deployment
• Return the composed URL for a deployed app after the deployversion and deployversionlight commands
• Modify the example app repos to use this URL to populate the URL link in the GitHub Actions
• Modify the example app repos to validate that the URL looks like what they expect before performing the deploy step