Use v1 endpoints for appservices

[Half-Shot]

Fixes #3780

This PR updates the prefix of all appservice endpoints to v1 to be inline with the AS spec. This change however is extremely breaking as currently all matrix-org bridges rely on the old behaviour. Comments welcome on how we could support both (not as simple as checking for 404s, as that's a valid response for some of these endpoints).

[richvdh]

@Half-Shot have you looked at what's wrong with the CI?

[Half-Shot]

Looking into it now.

[richvdh]

oh I see, you know this is a breaking change.

How about updating the AS config file to include the version of the AS API the AS supports?

(we'd need to make the requests by synapse actually match the specced format, as per #6457)

[Half-Shot]

How about updating the AS config file to include the version of the AS API the AS supports?

We could do, although since the registration file format is also part of the spec we would also need to spec that.

[Half-Shot]

With much sadness, I present matrix-org/matrix-spec-proposals#2379

[richvdh]

@Half-Shot are you still interested in working on this? what's the situation?

[Half-Shot]

Yes, need to figure out what I'm doing with matrix-org/matrix-spec-proposals#2379

[erikjohnston]

I'm going to close this as it appears blocked on the MSC