Yielding output is not verified

[JeremyPansier]

• [ ] A transaction holding an yielding output must be signed by the incomed output recipient.
• [ ] A yielding utxo must be updated when the recipient is not registered anymore.

  for address := range blockchain.registeredAddresses {
      isPohValid, err := blockchain.registry.IsRegistered(address)
      if err != nil {
          return fmt.Errorf("failed to get proof of humanity: %w", err)
      }
      if isPohValid {
          addedRegisteredAddresses = append(addedRegisteredAddresses, address)
      } else {
          removedRegisteredAddresses = append(removedRegisteredAddresses, address)
          for _, utxo := range blockchain.utxosByAddress[address] {
              if utxo.IsYielding() {
                  //utxo.ChangeExpiration
              }
          }
      }
  }