correct behaviour of groups after admin left the group

[kristinew]

on android client currently group members can continue chatting also when the admin left the group (and the group should be closed)

• check behaviour on iOs
• talk to Pavel how it should be

[monolar]

This is actually something new to me. Currently i see no reason why group members should be unable to chat in this case. But the group is basically orphaned and in an unclear state since the admin is gone and no new admin was declared. In this case two options are possible 1) We delete the whole group - not favored by me 2) The last remaining admin cannot leave the group - requires that we implement multi-admin group throughout the system and clients. We are nearly there and this is a reasonably achievable goal.