When enabling the account validity feature, Synapse will look at startup for registered account without an expiration date, and will set one equals to 'now + validity_period' for them. On large servers, it can mean that a large number of users will have the same expiration date, which means that they will all be sent a renewal email at the same time, which isn't ideal.
In order to mitigate this, this PR allows server admins to define a 'max_delta' so that the expiration date is a random value in the [now + validity_period ; now + validity_period + max_delta] range. This allows renewal emails to be progressively sent over a configured period instead of being sent all in one big batch.
If account validity is enabled in the server's configuration, this job will run at startup as a background job and will stick an expiration date to any registered account missing one.
We checked that 3pids were not already in use before we checked if
we were going to return the account previously registered in the
same UI auth session, in which case the 3pids will definitely
be in use.
https://github.com/vector-im/riot-web/issues/9586
Prevents a SynapseError being raised inside of a IResolutionReceiver and instead opts to just return 0 results. This thus means that we have to lump a failed lookup and a blacklisted lookup together with the same error message, but the substitute should be generic enough to cover both cases.
This allows the client to complete the email last which is more
natual for the user. Without this stage, if the client would
complete the recaptcha (and terms, if enabled) stages and then the
registration request would complete because you've now completed a
flow, even if you were intending to complete the flow that's the
same except has email auth at the end.
Adding a dummy auth stage to the recaptcha-only flow means it's
always unambiguous which flow the client was trying to complete.
Longer term we should think about changing the protocol so the
client explicitly says which flow it's trying to complete.
https://github.com/vector-im/riot-web/issues/9586
