fix(azure-registry): handle binary files

[lukaspj]

Hi!

The issue

We had an issue with fetching certificates from the Azure KeyVaults.
Because the certificate were binary files, the Azure KeyVault would base64 encode it, however the @azure/keyvault-secrets library gives no notice or way to detect that the secret is base64 encoded.

Then kubernetes-external-secrets would base64 encode it again, so the binary files were base64 encoded twice, which meant that we had to alter our application to base64 decode the certificates before we could use them.

This change

Here we add a new keyOptions field isBinary so that you can explicitly specify that the Azure KeyVault secret is a binary and that no base64 encoding should happen.

Notice that the isBinary field does not work together with the property field, as the property field does JSON-decode and that would definetly not work on a Buffer.

[silasbw]

thanks for tracking this down and submitting a fix!

[silasbw]

Thanks for the tracking this down and submitting the PR 💯 !