Allow installing into global-operator group

[kouk]

The possibleInstallModes method doesn't deal with the special case of a target namespace being the empty string, so validation fails when installing to the global operator group. E.g.

❯ kubectl operator install cert-manager --channel stable --approval Automatic -n operators
failed to install operator: operator "cert-manager" not installable: install modes supported by operator ("AllNamespaces") not compatible with install modes supported by existing operator group ("SingleNamespace")

Add a special method to determine the operator group's supported methods. Ref: https://olm.operatorframework.io/docs/concepts/crds/operatorgroup/#installmodes-and-supported-operatorgroups

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[kouk]

/assign @joelanford

[joelanford]

Hi @kouk, I think the issue you were experiencing may have been solved by https://github.com/operator-framework/kubectl-operator/pull/80

On a build from main, I retried your command and got this:

$ kubectl operator install cert-manager --channel stable --approval Automatic -n operators
subscription "cert-manager" created
operator "cert-manager" installed; installed csv is "cert-manager.v1.10.2"

I'm going to close this out since it looks like its fixed, but please open another issue or PR if you see something else missing!

[kouk]

thanks @joelanford I can't check it right now but seems legit.