Sign a message using a managed wallet. Managed wallet means the private key is never exposed to the client and always stored encrypted in our vault.
public_token.Authorization: Bearer {api_key}sol_signMessage.sol_signMessage).encoding is omitted, the message is interpreted as plaintext (utf-8).encoding is omitted, the response encoding defaults to base58.encoding is provided, the response uses the same encoding as the request but will be base64 or base58.