Rust serializing issue

cargo.toml

[package]
name = "serialize-gist"
version = "0.1.0"
edition = "2021"

[dependencies]
reqwest = { version = "0.12.5", features = ["json"] }
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0"
mev-rs = { git = "https://github.com/ralexstokes/mev-rs", tag = "v0.4.0-alpha.6" }
mockito = "1.5.0"
beacon-api-client = { git = "https://github.com/ralexstokes/ethereum-consensus"}
tokio = { version = "1.0", features = ["full"] }

main.rs

use beacon_api_client::VersionedValue;
use mev_rs::types::{AuctionContents, SignedBuilderBid};
use serde_json::json;

fn main() {}

async fn make_request(relay: String) -> Option<AuctionContents> {
    println!("Getting payload from relay: {}", relay);
    let relay = relay.clone();

    let url = format!("{}/eth/v1/builder/blinded_blocks", relay);
    let client = reqwest::Client::new();
    let client = reqwest::Client::new();
    let res = client
        .post(url.clone())
        .header("Content-Type", "application/json")
        .body(json!({}).to_string())
        .send()
        .await;
    if res.is_err() {
        println!("Failed to get payload from relay: {}", url);
        return None;
    }
    let res = res.unwrap();
    if !res.status().is_success() {
        println!("Failed to get payload from relay: {}", url);
    }

    let result: Result<VersionedValue<AuctionContents>, reqwest::Error> =
        res.json::<VersionedValue<AuctionContents>>().await;
    match result {
        Ok(result) => Some(result.data),
        Err(err) => {
            println!("err: {:?}", err);
            return None;
        }
    }
}

#[cfg(test)]
mod tests {

    use super::*;
    use mockito;
    use serde_json::json;

    #[tokio::test]
    async fn test_make_request() {
        let mut external_relay_server = mockito::Server::new_async().await;
        let external_relay_mock = external_relay_server
        .mock("POST", "/eth/v1/builder/blinded_blocks")
        .with_status(200)
        .with_header("Content-Type", "application/json")
        .with_body(
            json!({
                "version": "deneb",
                "data": {
                  "execution_payload": {
                    "parent_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
                    "fee_recipient": "0xabcf8e0d4e9587369b2301d0790347320302cc09",
                    "state_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
                    "receipts_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
                    "logs_bloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
                    "prev_randao": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
                    "block_number": "1",
                    "gas_limit": "1",
                    "gas_used": "1",
                    "timestamp": "1",
                    "extra_data": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
                    "base_fee_per_gas": "1",
                    "blob_gas_used": "1",
                    "excess_blob_gas": "1",
                    "block_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
                    "transactions": [
                      "0x02f878831469668303f51d843b9ac9f9843b9aca0082520894c93269b73096998db66be0441e836d873535cb9c8894a19041886f000080c001a031cc29234036afbf9a1fb9476b463367cb1f957ac0b919b69bbc798436e604aaa018c4e9c3914eb27aadd0b91e10b18655739fcf8c1fc398763a9f1beecb8ddc86"
                    ],
                    "withdrawals": [
                      {
                        "index": "1",
                        "validator_index": "1",
                        "address": "0xabcf8e0d4e9587369b2301d0790347320302cc09",
                        "amount": "32000000000"
                      }
                    ]
                  },
                  "blobs_bundle": {
                    "commitments": [
                      "0x8dab030c51e16e84be9caab84ee3d0b8bbec1db4a0e4de76439da8424d9b957370a10a78851f97e4b54d2ce1ab0d686f"
                    ],
                    "proofs": [
                      "0xb4021b0de10f743893d4f71e1bf830c019e832958efd6795baf2f83b8699a9eccc5dc99015d8d4d8ec370d0cc333c06a"
                    ],
                    "blobs": [
                      "0x24564723180fcb3d994104538d351c8dcbde12d541676bb736cf678018ca4739"
                    ]
                  }
                }
              })
            .to_string(),
        )
        .create_async()
        .await;
        let auction_contents = make_request(external_relay_server.url()).await;
        assert!(auction_contents.is_some());
    }
}