Allow using escaped commas in tag values

[RomanBednar]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Allows using commas in tag values; commas are allowed according to documentation.

Which issue(s) this PR fixes:

Fixes #1809

Special notes for your reviewer:

Tested with unit tests and manually as shown below:

Escaped commas with a backslash (\):

$ oc -n openshift-cluster-csi-drivers get deployment.apps/gcp-pd-csi-driver-controller -o json | jq '.spec.template.spec.containers[0].args[-1]'
"--extra-tags=openshift-gce-devel/rbednar-test-tag1/rbednar-test-value1,openshift-gce-devel/rbednar-test-tag2/value\\,with\\,comma"

CSI Driver created volume successfully:

I0819 13:12:36.831245       1 utils.go:69] /csi.v1.Controller/CreateVolume called with request: name:"pvc-6c6a18fc-e37e-4cae-8f7b-63042bbfc664" capacity_range:<required_bytes:2147483648 > volume_capabilities:<mount:<fs_type:"ext4" > access_mode:<mode:SINGLE_NODE_WRITER > > parameters:<key:"csi.storage.k8s.io/pv/name" value:"pvc-6c6a18fc-e37e-4cae-8f7b-63042bbfc664" > parameters:<key:"csi.storage.k8s.io/pvc/name" value:"pvc-2" > parameters:<key:"csi.storage.k8s.io/pvc/namespace" value:"default" > parameters:<key:"replication-type" value:"none" > parameters:<key:"type" value:"pd-standard" > accessibility_requirements:<requisite:<segments:<key:"topology.gke.io/zone" value:"us-central1-a" > > requisite:<segments:<key:"topology.gke.io/zone" value:"us-central1-b" > > requisite:<segments:<key:"topology.gke.io/zone" value:"us-central1-c" > > preferred:<segments:<key:"topology.gke.io/zone" value:"us-central1-c" > > preferred:<segments:<key:"topology.gke.io/zone" value:"us-central1-a" > > preferred:<segments:<key:"topology.gke.io/zone" value:"us-central1-b" > > >
...
I0819 13:12:40.728527       1 controller.go:715] CreateVolume succeeded for disk Key{"pvc-6c6a18fc-e37e-4cae-8f7b-63042bbfc664", zone: "us-central1-c"}

Tag has been added correctly to provisioned disk:

Does this PR introduce a user-facing change?:

Driver now allows users to include commas (,) in tag values. If used, commas must be escaped with a backslash (\).

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[mattcary]

Why can't we just do
case escaped:
if r != escape {
buf.WriteRune(r)
escaped = false
}

I think the current code will do the wrong thing on foo,,bar.

also I think both versions of the code do the wrong thing on foo\,bar, usually that would escape the backslash and not escape the comma, but here this is turned into an escaped comma?

[RomanBednar]

@mattcary You're right, it can be simplified as suggested. As for the behavior of escaping, what do you think the correct behavior should be? Or which unit test is wrong specifically?

In case of foo,,bar input splitWithEscape will output "foo", "", "bar" which will later fail validation as it's not a valid format for a tag here:

gcp-compute-persistent-disk-csi-driver/pkg/common/utils.go

Line 322 in afdbb01

return nil, fmt.Errorf("tag %q is invalid, correct format: 'parent_id1/key1/value1,parent_id2/key2/value2'", parentIDkeyValueString)

here this is turned into an escaped comma?

I think you could say that, it's actually the intention of this change to allow users escaping the commas somehow so they can be used in tag value (as documented). Maybe there's a better solution?

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