Introduction of a global resource limit

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Is your feature request related to a problem? Please describe.
Tenama already supports limiting the maximum namespace size that can be provisioned via API call. However, cluster resources could be consumed by creating many namespaces.

Since from my point of view the use-cases of Tenama are the access and provisioning of temporary namespaces in a namespace-based shared cluster environment, this behavior could also affect other services on the cluster.

Describe the solution you'd like
Therefore, Tenama should also offer the possibility to configure a global limit over all created namespaces in the future.

I would define the resources the same way on a requests and limits basis and extend namespace creation logic so that tenama checks in advance if the sum of the resource quotas of all namespaces created by tenama that currently exist in the cluster + the new namespace exceed the global quota.

Probably the simplest variant would be to reject the call with a meaningful message and motivate the client to retry at a later time.

Describe alternatives you've considered

Alternatively, we could include a volatile internal queue in Tenama that attempts to create via FIFO the namespaces that would currently exceed the global quota. Of course, this could lead to very long queues if the user sets the lifetime of the namespaces to a "long" time.
Additionally, the client would have to be notified somehow afterwards about the successful creation, otherwise we would end up with long synchronous calls and I don't think that's good.

Additional context
Add any other context or screenshots about the feature request here.