Add m.id_access_token flag

[anoadragon453]

Adds a flag to /versions' unstable_features section indicating that this Synapse understands what an id_access_token is, as per #5927 (comment)

Fixes #5927

[richvdh]

assuming that we do indeed support the features indicated by the flag, lgtm

[richvdh]

(could you link to the PR(s) which added the relevant support, for future reference?)

[jryans]

(could you link to the PR(s) which added the relevant support, for future reference?)

For Riot Web at least, this was done in matrix-org/matrix-js-sdk#1022.
For Riot iOS, work is in progress under element-hq/element-ios#2603.
For Riot Android, work has not yet happened yet under element-hq/riot-android#3228.

[anoadragon453]

@richvdh Assume you want to wait for this to merge before MSC'ing happens?

[anoadragon453]

And speaking of which, the MSC has gone into FCP: matrix-org/matrix-spec-proposals#2264

[richvdh]

(could you link to the PR(s) which added the relevant support, for future reference?)

For Riot Web at least, this was done in matrix-org/matrix-js-sdk#1022.
For Riot iOS, work is in progress under vector-im/riot-ios#2603.
For Riot Android, work has not yet happened yet under vector-im/riot-android#3228.

Thanks for this, but I was really looking for where the synapse support was added...

[anoadragon453]

Oh you mean where we accept the id_access_token parameter?

That is added as part of #5892