get
https://n/a/ethereum/message/request-refund
Generates a challenge message for the custodian to sign, confirming their intent to refund ETH locked in the smart contract due to failed validator creation.
The response includes a unique id (nonce) and a human-readable message.
The custodian must sign this message using their private key (corresponding to the walletAddress)
and submit the signature to the refund submission endpoint to authorize the operation.