Feature Request: support diskEncryptionKey/KmsKey for google batch executor

[livanaz]

Hi Nextflow Team,

Google batch and Compute Engine can use disks that support a customer managed encryption key(https://cloud.google.com/kms/docs/cmek). Is it possible to add this feature to nextflow?

Thank you!

Best,

[pditommaso]

Feel free to provide a pull request for it.