Add openapi schema for proper patching of CRDs

[larsks]

Due to issues with the way Kustomize handles patching lists in custom
resource types, we need to provide a complete OpenAPI schema that
includes schema definitions for any CRDs we wish to patch.

See cluster-scope/base/openapi/README.md for more information.

[computate]

@larsks is the openshift-api-schema.json file specific to a certain cluster? What if we want to patch a GrafanaDataSource CRD on the upcoming observability cluster that doesn't manage secrets well and requires the Patch Operator:

apiVersion: integreatly.org/v1alpha1
kind: GrafanaDataSource

[larsks]

is the openshift-api-schema.json file specific to a certain cluster?

It is not. It needs to be a superset of the resources available in all of our clusters (at least those we want to patch).

What if we want to patch a GrafanaDataSource CRD on the upcoming observability cluster that doesn't manage secrets well and requires the Patch Operator:

Then we would need to add the appropriate schemas to the file.

---

I've partly addressed this in the README:

To support this, that means we need to dump the complete openapi schema
from our clusters to a file and make that available to Kustomize. This
commit introduces an initial version of this schema, but we will need
to update this in the future whenever we want to patch CRDs that
weren't available at the time we last generated this schema dump.

[larsks]

I've had a change of heart about how to implement this; I've moved all the sausage making to https://github.com/nerc-project/openshift-schemas; the generated schema is included here by URL.

[computate]

That new repo is very clever, I like your sausage recipe.