Set user's displayname and avatar URL to avoid ugly join-then-set sequencing, and placate SYN-787
Set user's displayname and avatar URL to avoid ugly join-then-set sequencing, and placate SYN-787

matrix-org/matrix-appservice-slack,matrix-org/matrix-appservice-slack,matrix-org/matrix-appservice-slack,matrix-org/matrix-appservice-slack