Support Client-Server API r0.6

[anoadragon453]

We should remove the unstable feature flags that were part of the r0.5.0 release cycle. These are:

• m.require_identity_server (Add m.require_identity_server to /versions unstable_flags #5972)
• m.id_access_token (Add m.id_access_token to /versions unstable_features (MSC2264) #5974)
• m.separate_add_and_bind (Add an unstable feature flag for separate add/bind 3pid APIs #6044)

Clients that rely on these flags should check for Client Server API r0.6.0 support instead.

We should remove all the deprecated endpoints. These are:

• /account/3pid - replaced by /account/3pid/add and /account/3pid/bind
• Others...

[anoadragon453]

What about the lazy-loading flag (m.lazy_load_members)? :)

[turt2live]

LL is dependent on #5528

[jryans]

@anoadragon453, does the backend team intend to also remove the unstable API prefix from 3pid/unbind as part of supporting r0.6.0? This is what the new spec process (from MSC2324) would suggest, but the feature was added before that process appeared, so I am unsure what process will be followed and when clients needs to follow along.

[jryans]

From chatting with @neilisfragile, it sounds like we will indeed apply the new spec process here with the 2 month window before removing unstable.

[turt2live]

Dropped this down to just r0.6 as .1 is coming out soon.

@anoadragon453 any update on this? It's been well over 2 months and I'm tempted to start shipping air horns with GPS triggers to the UK until this get resolved.

[turt2live]

@richvdh why was this closed? It's still an issue.

[turt2live]

answer: github mobile is terrible at showing it was closed by a PR.