update backupbucket fields

[kon-angelo]

How to categorize this PR?

/area control-plane
/kind enhancement
/platform azure

What this PR does / why we need it:
Publish the BackupBucket domain name, to enable different Azure landscapes.
See: gardener/etcd-backup-restore#756

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Release note:

The BackupBucket controller now adds an additional field in the generated secret to indicate the blob storage service domain. This can be used to create blobs in other Azure environments like CN or USGov.

[unmarshall]

Minor comments

[unmarshall]

Is it possible to make constants for these? (It is a pity that designers of the SDK do not think of these things)

const (
  BlobStoreGlobalDomain = "blob.core.windows.net"
  BlobStoreChinaDomain = "blob.core.chinacloudapi.cn"
  BlobStoreUSGovDomain = "blob.core.usgovcloudapi.net"

[unmarshall]

you can club 2 cases into 1:

case cloudConfiguration == nil:
case strings.EqualFold(cloudConfiguration.Name, "AzurePublic"):
  return "blob.core.windows.net", nil

[renormalize]

fallthrough must be used to achieve this functionality in Go, but there's a more idiomatic way of doing this.

case cloudConfiguration == nil, strings.EqualFold(cloudConfiguration.Name, "AzurePublic"):
    return "blob.core.windows.net", nil

[kon-angelo]

I think that you would need to use fallthrough for that. Also in a very recent PR of mine in gardener core, they voted to merge conditions by ||. I will probably do the same here for coherence

[unmarshall]

If you look at the azure-sdk-for-go the nomenclature is a bit different. They provide 3 different clients AFAIK:

1. Blob client which is created with a specific blob URL (see here)
2. Container client which is created for a specific container/bucket ( see here).
3. Service client to manage buckets/containers (see here)

So what you have here is a ContainerClient or a BucketClient but you call it a blobClient. This confused me a bit.

[kon-angelo]

I had to look closer for that one. The blob client that we use, creates all the clients internally, so e.g. from the interfaces that we use the azure SDK does something like:

func (c *Client) DeleteBlob(ctx context.Context, containerName string, blobName string, o *DeleteBlobOptions) (DeleteBlobResponse, error) {
	return c.svc.NewContainerClient(containerName).NewBlobClient(blobName).Delete(ctx, o)
}

So from our perspective we only use the top level interfaces and all the container/bucket client is hidden from us - I guess that's why the name was blobClient. I will think how to do the names better.

[kon-angelo]

/hold

[kon-angelo]

tested with http://europe-docker.pkg.dev/gardener-project/snapshots/gardener/etcd-druid:v0.22.4-dev-c692c9db187df47bc45c2d9815e5e31108b30faf successfully.

/unhold