Add support for OVH KMS in SOPS

[arunbhagyanath]

This PR adds support for encrypting and decrypting files using OVH Key Management Service.

Usage

export OVH_CERTIFICATE_FILE=/path/to/cert.pem
export OVH_CERTIFICATE_KEY_FILE=/path/to/key.pem

sops --ovh-kms "<rest-endpoint>/<your-key-id>" -e file.yaml > file.enc.yaml
sops -d file.enc.yaml

NB: Recreating the PR

[felixfontein]

Hi @arunbhagyanath, I'm pretty sure I did not author this commit, as the commit metadata claim :) Can you please fix the commit? Thanks. (Probably the easiest way is to do git reset --soft HEAD^ in the branch, git commit --sign-off it again, and force push.)

[arunbhagyanath]

Hi @arunbhagyanath, I'm pretty sure I did not author this commit, as the commit metadata claim :) Can you please fix the commit? Thanks. (Probably the easiest way is to do git reset --soft HEAD^ in the branch, git commit --sign-off it again, and force push.)

Yea, should be good now

[arunbhagyanath]

@felixfontein, Is there anything blocking a merge?

[felixfontein]

@arunbhagyanath sorry for the late response, it's basically still this: #1097 (comment)