Function create_nip98_authorization_for_payload_hash 

pub fn create_nip98_authorization_for_payload_hash(
    identity: &LocalIdentity,
    method: &str,
    url: &str,
    payload_sha256: &str,
    created_at: u64,
) -> Result<HttpAuthorizationPlan, SoftchatError>

Create a NIP-98 plan from a SHA-256 produced while streaming a request body.

This is the production attachment-upload path: platform HTTP/file code streams the body, then passes its lowercase hexadecimal digest without copying the full payload across FFI.

Errors

Returns SoftchatError::InvalidHttpAuthorization for an invalid method, URL, digest, timestamp, or signing failure.