// GetDisplayName returns the display name of the user from the specified MXID. See https://matrix.org/docs/spec/client_server/r0.2.0.html#get-matrix-client-r0-profile-userid-displayname
// GetOwnDisplayName returns the user's display name. See https://matrix.org/docs/spec/client_server/r0.2.0.html#get-matrix-client-r0-profile-userid-displayname
// SetDisplayName sets the user's profile display name. See http://matrix.org/docs/spec/client_server/r0.2.0.html#put-matrix-client-r0-profile-userid-displayname