Merge #159: chore(submit_package): use unwrap_or_default instead of .unwrap()

ea9b5d1 refactor(blocking): propagate `hex-conservative` errors instead of `.unwrap()`. (Leonardo Lima)
c2c5485 refactor(submit_package): use `unwrap_or_default` instead of `.unwrap()` (Leonardo Lima)

Pull request description:

  ### Description

  - use `unwrap_or_default()` instead of `.unwrap()`, ideally it should return a specific error variant, it'd be a breaking change though and can be added in a follow-up.
  - it's only possible to use the internal `minreq::Error` to wrap the `serde_json::Error`, but not the `reqwest::Error` as it does not have public constructors.

  ### Notes to the reviewers

  I personally wanted to remove the `.unwrap()` and properly handle the error, though the options I had in mind:
  - (i) adding a new `SerdeJson` variant is a breaking change; we can do it as a follow-up for 0.13.0
  - (ii) mapping and wrapping it into either minreq/reqwest errors is only possible in minreq, so I thought it's better to keep it standard and use `.unwrap_or_default()` on both for now.

ACKs for top commit:
  luisschwab:
    ACK ea9b5d1
  ValuedMammal:
    ACK ea9b5d1

Tree-SHA512: 860e9351e256b8bd494d6cac259986b20b2e97c4955abce5cbe1663f47df48665262d440954899177c2482377d2ef558cd8fe6d32f635b61b3ba2be1e03a92ae

Author: oleonardolima

src/async.rs

@@ -410,7 +410,7 @@ impl<S: Sleeper> AsyncClient<S> {
         let response = self
             .post_request_bytes(
                 "/txs/package",
-                serde_json::to_string(&serialized_txs).unwrap(),
+                serde_json::to_string(&serialized_txs).unwrap_or_default(),
                 Some(queryparams),
             )
             .await?;

src/blocking.rs

@@ -144,7 +144,7 @@ impl BlockingClient {
             }
             Ok(resp) => {
                 let hex_str = resp.as_str().map_err(Error::Minreq)?;
-                let hex_vec = Vec::from_hex(hex_str).unwrap();
+                let hex_vec = Vec::from_hex(hex_str)?;
                 deserialize::<T>(&hex_vec)
                     .map_err(Error::BitcoinEncoding)
                     .map(|r| Some(r))
@@ -162,7 +162,7 @@ impl BlockingClient {
             }
             Ok(resp) => {
                 let hex_str = resp.as_str().map_err(Error::Minreq)?;
-                let hex_vec = Vec::from_hex(hex_str).unwrap();
+                let hex_vec = Vec::from_hex(hex_str)?;
                 deserialize::<T>(&hex_vec).map_err(Error::BitcoinEncoding)
             }
             Err(e) => Err(e),
@@ -332,9 +332,8 @@ impl BlockingClient {
         let mut request = self.post_request(
             "/txs/package",
             serde_json::to_string(&serialized_txs)
-                .unwrap()
-                .as_bytes()
-                .to_vec(),
+                .unwrap_or_default()
+                .into_bytes(),
         )?;
 
         if let Some(maxfeerate) = maxfeerate {