As a Steward, I need to have a script that can generate Proof of possession for my BLS key, so that I can use this value in a NODE txn

Each Steward must send a NODE txn with Proof of Possession of his BLS keys. So, we need a script that can help in generating the transaction.

Acceptance criteria

• Create a script in Indy-node: `generate_bls_proof_of_posession`

• • the script need to be installed with Indy Node
  • Input for the script: no
  • Output:
    • BLS Public key in a form to be sent in NODE txn (base58-encoded)
    • BLS Proof of possession for the Public Key in a form to be sent in NODE txn (base58-encoded)