how to find the applicationURL of a deployment programmatically

Summary:

hi, i'd like to include the url of the deployed application in an email (e.g. to let the user click to open the page) … could i ask what's the best way to get that url (i.e. the equivalent of applicationURL) from the application programmatically, rather than hard coding it? (since it'd be nice not to have to change the setting on each deployment). I note that $application.path contains that, plus the name of the folder for resources. But it'd be nice to get the applicationURL directly.

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