Activate pending subkey
Activate a pending subkey by providing a Starknet signature
over pedersen(timestamp, eph_public_key).
Activate a pending subkey by providing a Starknet signature
over pedersen(timestamp, eph_public_key).
Starknet signature [r, s] over pedersen(timestamp, eph_public_key).
Unix timestamp (seconds) included in signed message.
Optional: New name for the subkey upon activation.