mod_rest/rest.sh: Update to use httpie-oauth2 plugin This bash implementation of OAuth2/OIDC was growing to the point where it needed a massive refactor, which made me look into alternatives where I finally settled on implementing oauth2 in a plugin for HTTPie.

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```