Simulate dev / staging / production deployments via deployment flag #233
Description
Raised by @gergelyk (spinframework/spin#3370):
During development I would like to deploy my app to an unofficial environment (dev or staging) where I can test it without affecting the users. Only when I'm sure that the new version is ready, I would like to deploy it to the official environment/domain.
Until now I was simply changing the name of my app in the spin.toml file. E.g. myapp is the name that results in official deployment and myapp-staging would be deployed separately.
I thought that it could be convenient to introduce a CLI argument to achieve this without modifying spin.toml.