Remove platform tenancy from SXCHNGE customer BFF (#34)

backend/pkg/merrors/errors.go

@@ -223,12 +223,6 @@ func Unauthorizedf(format string, args ...any) error {
 	return Unauthorized(fmt.Sprintf(format, args...))
 }
 
-var ErrNoMessagingTopic = Define("messagingTopicError")
-
-func NoMessagingTopic(topic string) error {
-	return Wrapf(ErrNoMessagingTopic, "messaging topic '%s' not found", topic)
-}
-
 func InvalidArgumentWrap(err error, msg string, argumentNames ...string) error {
 	return wrapError(ErrInvalidArg, invalidArgumentMessage(msg, argumentNames...), err)
 }