Determine necessary features for running standalone in prod

[cloutiertyler]

We want it to be reasonable for small-scale users to self-host SpacetimeDB-standalone in production, but we haven't really done the work of determining what's necessary to get there.

Notably, someone in the Discord asked about restricting who can publish. It's obviously undesirable for anyone to be able to publish modules to a production STDB instance which is meant to be serving a single app.

I'm sure there are many other features we're missing. Probably we can crowdsource the list.

Assigning this to the UX team because it's a matter of determining users' needs.