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.
This commit adds two config options:
* `restrict_public_rooms_to_local_users`
Requires auth to fetch the public rooms directory through the CS API and disables fetching it through the federation API.
* `require_auth_for_profile_requests`
When set to `true`, requires that requests to `/profile` over the CS API are authenticated, and only returns the user's profile if the requester shares a room with the profile's owner, as per MSC1301.
MSC1301 also specifies a behaviour for federation (only returning the profile if the server asking for it shares a room with the profile's owner), but that's currently really non-trivial to do in a not too expensive way. Next step is writing down a MSC that allows a HS to specify which user sent the profile query. In this implementation, Synapse won't send a profile query over federation if it doesn't believe it already shares a room with the profile's owner, though.
Groups have been intentionally omitted from this commit.
Brendan Abolivier