fixes #9611 (#9664)

app/plugin_api.go

@@ -306,6 +306,10 @@ func (api *PluginAPI) GetChannelMembers(channelId string, page, perPage int) (*m
 	return api.app.GetChannelMembersPage(channelId, page, perPage)
 }
 
+func (api *PluginAPI) GetChannelMembersByIds(channelId string, userIds []string) (*model.ChannelMembers, *model.AppError) {
+	return api.app.GetChannelMembersByIds(channelId, userIds)
+}
+
 func (api *PluginAPI) UpdateChannelMemberRoles(channelId, userId, newRoles string) (*model.ChannelMember, *model.AppError) {
 	return api.app.UpdateChannelMemberRoles(channelId, userId, newRoles)
 }