Proposal: Add Support for SOPS_AGE_SSH_PRIVATE_KEY_CMD Environment Variable

[natescherer]

Hello!
I am really loving sops, and I've been working on getting it integrated with the 1Password CLI via the SOPS_AGE_KEY_CMD environment variable. However, I (like a lot of people I imagine) am deriving my age key from my SSH private key, and it occurred to me that the age key derivation step could be cut out if a SOPS_AGE_SSH_PRIVATE_KEY_CMD environment variable could be added and set up to work similarly to SOPS_AGE_KEY_CMD.

Would there be interest in accepting this? If so, I'm happy to work on a PR.

[uncenter]

Would love to see this myself, I am having the same problem where I want to use my 1Password-stored SSH key. @natescherer if you're still willing and able, a pull request might help move this along?

[natescherer]

@uncenter Just created #2070 for this!