Don't show 'Invite members' if email is not set up

[matthewelwell]

Currently the 'Users and permissions' screen in organisation settings will show the 'Invite members' button (which triggers an email invite) regardless of whether email configuration has been added to the API.

We have a couple of options to solve this:

1. If the FE receives an error when sending an invite, then show a dialog recommending that they use invite links instead
2. The API can add an attribute to e.g. the version endpoint which indicates whether email configuration has been added or not. If not, the FE can disable the button and show a tooltip.

The preference here is likely (2), but I did enjoy the experience from Metabase which is more along the lines of (1).

[kyle-ssg]

I think 1 only works if entering the email and submitting does something useful, in Metabase's case it creates the user and assigns a password I think?

If we just handled failed submissions then entering the email would have been pointless in the first place, I think 2 is more suitable unless we did something with the entered email e.g. prefil the login/signup form or attempt to create the user.