Enforcing max cluster and max node settings within a tenant.

Trying to create a cluster that violates the max will cause the
request to fail with a 409. Similarly, trying to lower the max
below whats already in use will cause the request to fail with a
409.
The reasoning behind failing the request in this case is that setting a maximum implies intent for that to be a hard maximum.  If you are able to lower the max below what is in use now, what was the point of setting the max that low to begin with?