Support inviting other people to Zulip

[gnprice]

It'd be good for the mobile app to provide the feature of inviting other people to your Zulip organization. Here's the existing user docs for the feature, as found in the webapp (and desktop app):
https://zulipchat.com/help/invite-new-users

Recording this now because a user asked about it today in chat. We haven't to date considered this a priority; it's generally an infrequent thing to need to do, and people have been content to use the webapp or desktop app for it. But filing this issue gives us a place to track if we start hearing repeated requests from more people.

[chrisbobbe]

We haven't to date considered this a priority; it's generally an infrequent thing to need to do, and people have been content to use the webapp or desktop app for it.

We've noted at #3132 that onboarding is

an area where we're at high risk of not noticing an issue ourselves or hearing reports from users, because developers and enthusiastic users don't go through these flows in our own normal usage.

and

an area where issues can have an effect way out of proportion to the number of times a given user would run into them, because for a new user it's a big part of their experience with Zulip so far.

— so it's good to have this issue open. 🙂

[gnprice]

That is true! I think this isn't quite that kind of onboarding issue, though -- maybe "onboarding" isn't even the right label for it, but it's the closest we have. In particular, an enthusiastic user may well regularly want to invite people to their Zulip org, even though they don't (and can't 🙂) regularly use Zulip for the first time.