Support for the Provisioned Service defined in the Service Binding Specification for Kubernetes

**Describe the problem/challenge you have**

I want to use the `SecretTemplate` API with implementations of [the Service Binding Specification for Kubernetes](https://github.com/servicebinding/runtime).

**Describe the solution you'd like**

Make the `SecretTemplate` API a [Provisioned Service](https://servicebinding.io/spec/core/1.0.0/#provisioned-service) as defined in the Service Binding Specification for Kubernetes.

**Anything else you would like to add:**

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