[FR] - Add extended Pool Operator Signing/Verification Key Types

[gitmachtl]

As part of a desaster recovery or a lost hardware device, if you derive stake pool cold keys from mnemonics, you get extended ones.

Currently it looks like that the extended versions of both the secret key and the verification key are missing in the api/cli.

Those would be like:

{
      "type": "StakePoolExtendedSigningKey_ed25519_bip32",
      "description": "Stake Pool Operator Signing Key",
      "cborHex": "588078e35b66cbb23cbc623d81623e34ad157a667cfc4f843649236e7b7fb322b65b6d2c6afe2ebb5923875e776eaac1b21002253bb6b0003cc6a9d8c45ab5dd30995474de0dd906dae02e33cad45bb24a21f1ade6af57457b6ea171985412cd35d070a3adf6f2ecd799fa127e536d2c93c2c1946d11fb92c5608dfb3acef8eb72f1"
}

{
      "type": "StakePoolExtendedVerificationKey_ed25519_bip32",
      "description": "Stake Pool Operator Verification Key",
      "cborHex": "58405474de0dd906dae02e33cad45bb24a21f1ade6af57457b6ea171985412cd35d070a3adf6f2ecd799fa127e536d2c93c2c1946d11fb92c5608dfb3acef8eb72f1"
}

Those types should be added, so we can also use them normally with all pool key operations.

Also we don't have a bech specification yet in CIP-005 for the. The bech prefix pool_sk and pool_vk are only for normal ones, not extended ones.