3PID invites

[ara4n]

Related: #529

[kegsay]

Blocked on https://matrix.org/jira/browse/SYN-540

[kegsay]

Background:

• Client types in https URL for identity server, and client persists it.
• Client uses this for registration / 3PID linking.
• This URL cannot be used for 3PID invites.

So I was told to do the same request without https:// and it Should Work which isn't the most helpful thing ever. This is because HS -> IS traffic is always https so the protocol portion of the URI is redundant/ignored. I don't think clients should be responsible for maintaining two different representations of identity servers just because https is "mandated" on HS -> IS; it's a horrible leaky abstraction currently.

In the interest of speed however, I'll just bite the bullet and strip the protocol so this bug can be resolved, but I don't have to like it.

[kegsay]

After doing this, I now get 401d...

[kegsay]

Blocked on Synapse working as intended.

[kegsay]

So you can now invite users on 3PID if they have already linked their account, but now getting 500d if they do not have a Matrix account.

[kegsay]

So this is now fixed but I'm not getting an email to say I've been invited to a room..

[kegsay]

Blocked waiting for invites to send emails.

[kegsay]

Need to:

• Fix 3PID invite emails should provide a link to vector which encourages the user to sign up with the right email address #529 - just the new user bit, not the "already have an account so go to settings to bind a new email" for v0.
• Bind emails on registration on vector (just a flag on the request?)

[kegsay]

Fixed mentioned issues. See #529 for follow-on work post-v0.