Improve invitation flow

[rgoj]

This is, partially, a follow-up to #709 and #810 and the previous work on Auth0 login flows. Using libraries, solutions and extensions provided by Auth0 as much as possible has greatly simplified maintenance on our side and increased security. Great! However, there's still an unpleasant snag in the invitation flow - it's just now what you expect from an app in 2023!

Especially linking a Google account can be frustrating for users. We went for the 80/20 solution and used an exisiting Auth0 extension, but really it'd be great to implement a proper invitation flow. Hopefully we can move to an open source auth provider and do this work then.

Here's a particular support conversation that prompted me to write out this issue - there's a gem of a write-up of what confusion a user experiences trying to link their Google account after being invited into Maptio! Great as motivation to improve this flow.

Another issue with the current flow, even if you don't want to log in via Google, is that you have to go through a confusingly large number of login screens to be able to properly log in and the system doesn't clearly indicate what is actually happening.

[rgoj]

Here is another case of, it would seem, someone who got an invitation into Maptio and then ended up being locked out of the organisation because, naturally, they wanted to use # with google: https://app.intercom.com/a/inbox/q3x5lnhp/inbox/shared/all/conversation/106323200014068

Instead of getting into the organisation they were invited to, Maptio asked them to create a new organisation as if they were signing up, not responding to an invitation into an existing organisation.

[rgoj]

I see that I never mentioned above that I recorded this excruciatingly painfully embarrassing vide when this issue first came up in August, here it is and explains a bit of the context and shows what a convoluted process it is to get into Maptio and # with Google: https://www.loom.com/share/3d93b5b3c5f748b2a756ffd01c9d1111?sid=193dab4c-0a77-4993-b237-d687d82d78f7

[rgoj]

Another case here: https://app.intercom.com/a/inbox/q3x5lnhp/inbox/shared/all/conversation/106323200014667?view=List

[rgoj]

Another similar, though not entirely identical, issue here: https://app.intercom.com/a/inbox/q3x5lnhp/inbox/conversation/106323200014747

[rgoj]

One of the couple of issues mentioned above actually ended up leading to another issue today. When I was manually assigning a subscription, I mistakenly assigned it to an organisation that was created by a user who ended up creating a new account after receiving an invitation (and so there were a couple of organisations of the same name within intercom and I chose the incorrect one! probably also because I was half asleep, a +1 to finally automating subscriptions too!). Here's today's issue: https://app.intercom.com/a/inbox/q3x5lnhp/inbox/shared/all/conversation/106323200014864?view=List

[rgoj]

Another instance of someone unable to access the organisation they were invited into: https://app.intercom.com/a/inbox/q3x5lnhp/inbox/conversation/106323200015066

This time because they were invited with email "X" but then used "Log in with Google" with another email, making the solution not that obvious! Ha, another interesting case for a new invite system to handle, we'd have to somehow track what email is being used for login vs for the invite.

[rgoj]

Just happened again here: https://app.intercom.com/a/inbox/q3x5lnhp/inbox/conversation/106323200015482 and a past issue here caused a similar problem: https://app.intercom.com/a/inbox/q3x5lnhp/inbox/conversation/106323200015485

Ouch!

[rgoj]

Another similar issue here: https://app.intercom.com/a/inbox/q3x5lnhp/inbox/conversation/106323200020876