Support age1yubikeys in sops

[ajarara]

Sops: SOPS is an editor of encrypted files that supports YAML, JSON, ENV, INI and BINARY formats and encrypts with AWS KMS, GCP KMS, Azure Key Vault, age, and PGP.

I use sops as a way to distribute repo-embedded secrets to deployments. My current state is something like:

keys:
  # these pgp fingerprints are hypothetically stashed on yubikeys
  - &admin1 85D77543B3D624B63CEA9E6DBC17301B491B3F21
  - &admin2 E60892BB9BD89A69F759A1A0A3D652173B763E8F
  - &deploymentA age13g95t0knjaanph6s8d5qlt9e00pacjthrgjdt8hn0n32eqyt596qgxymrs

creation_rules:
  - key_groups:
      - pgp:
          - *admin1
          - *admin2
        age:
          - *deploymentA

I've generated age keys on yubikeys, and would like to use the following (so I can move off of gpg entirely : )

keys:
  # these are now hypothetical age keys!
  - &admin1 age1yubikey3kkk8fcv3x35nhumlpj6ljsl87mfet7weu73yx4m94twyfgrnvqqjtzkw
  - &admin2 age1yubikeylxh0t6yv38jxpgsvgf4vm74v6zy4d884j9mkh0er2lvshddduqassnsk
  - &deploymentA age13g95t0knjaanph6s8d5qlt9e00pacjthrgjdt8hn0n32eqyt596qgxymrs

creation_rules:
  - key_groups:
      - age:
          - *admin1
          - *admin2
          - *deploymentA

However sops secret.yaml chokes with:

failed to parse input as Bech32-encoded age public key: malformed recipient "age1yubikey1qfj6cjej7ghmgl06vffex7eefvajusr4lu9w8k2sfe089wv3z7gdvqw0jjj": invalid type "age1yubikey"

Sops calls in here:

https://github.com/getsops/sops/blob/a8fb5405533aa10c36e267a9410d9e8ac0cf7a3b/age/keysource.go#L299

It's unclear to me whether this is a sops ask or an age ask: my hunch is that it's age's responsibility to come up with a valid recipient for any available plugin implementations.