Invite user capability enabled by default even while smtp host is not configured

[talSofer]

Steps to reproduce

1. Create lakefs config file not including smtp server configurations
2. Go to Administration -> Users
3. Click "Invite user" and try to invite a user
4. you'll see the following error
   

The fix should be to disable it by default.

Impact: This bug also impacts lakefs playgrounds, where IMO the invite user capability should not be disabled.

[johnnyaug]

Does this happen when using an external authentication service? Or using the internal one?

[idanovo]

Does this happen when using an external authentication service? Or using the internal one?

I think it's happens in OSS so probably the internal one @johnnyaug