Spec compliance: require a request body on `POST /rooms/{roomId}/receipt/{receiptType}/{eventId}`

[reivilibre]

We currently don't require a body on POST /rooms/{roomId}/receipt/{receiptType}/{eventId}.

Initially, this seems to have been a mistake, but since #10531 [v1.40.0rc2], it's a workaround because Element Android relied on that behaviour (which we broke by actually using the body for hidden read receipts in #10413 [v1.40.0rc1]).

Blockers:

• Yell in Client Developers room now
• Element Android doesn't send a JSON body for POST /rooms/{roomId}/receipt/{receiptType}/{eventId} element-hq/element-android#3789
• Figure out how long Element Android needs to propagate, set target removal date
  Minimum of four weeks following release. Revisit in October.
• Wait x time for a fixed Android release to propagate

Eventually, we should return to enforcing the spec.

[richvdh]

I'd like us to set a timescale for deprecation of this workaround while it's still fresh in our heads.

[callahad]

Fixed in Element Android this week, will be in EA 1.2.1. Have asked for an estimate of user uptake so we can figure out a timeline and will report back once I know.

I've also mentioned this anticipated change in the Matrix Client Developers room.

[callahad]

General feeling is "the longer the better" for Android uptake, but at least 4-6 weeks. We should watch traffic on matrix.org to confirm.

[richvdh]

Thanks Dan. Let's revisit this at the end of October in the hope that we will feel comfortable fixing it then?

[reivilibre]

"the longer the better" for Android uptake

yeah, especially considering F-Droid (the builds lag behind a bit and generally require manual updating).
I'm certainly guilty of not updating for weeks (though it's also likely that F-Droid users will tend to know how to fend for themselves a bit, and realise that updating might fix bugs)...