Consistent error wrapping (#30600)

server/channels/app/channel.go

@@ -1552,7 +1552,7 @@ func (a *App) addUserToChannel(c request.CTX, user *model.User, channel *model.C
 	if channel.IsGroupConstrained() {
 		nonMembers, err := a.FilterNonGroupChannelMembers([]string{user.Id}, channel)
 		if err != nil {
-			return nil, model.NewAppError("addUserToChannel", "api.channel.add_user_to_channel.type.app_error", nil, "", http.StatusInternalServerError)
+			return nil, model.NewAppError("addUserToChannel", "api.channel.add_user_to_channel.type.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
 		}
 		if len(nonMembers) > 0 {
 			return nil, model.NewAppError("addUserToChannel", "api.channel.add_members.user_denied", map[string]any{"UserIDs": nonMembers}, "", http.StatusBadRequest)