Extend MembershipUpdateEvent with members details (displayName, image, etc.)

[osmaczko]

Problem

Some members in group-chat may have unknown details, as in the attached picture:

It happens because it is not guaranteed that user receives each member's ContactCodeAdvertisement in time.

Solution

Extend MembershipUpdateEvent with members details (displayName, image, etc.).

Users can only add mutual contacts to the group, meaning they should already have all details about them (displayName, image, etc.). These details should be propagated to other members of the group so that they don't need to wait for ContactCodeAdvertisements of certain members.

[cammellos]

I think extending membership update would be very expensive in terms of bandwidth, this is a case where probably we want to find an alternative solution, what do you think?