Allow receiver to set minimum fee_rate

    Payjoin receiver can set minimum `fee_rate`
    in order to reject payjoin requests that contain
    a psbt which doesnt meet the minimum `fee_rate`
    threshold.

    We add this functionality to `check_broadcast_suitability`
    function which previously was called `check_can_broadcast`.

payjoin/src/receive/mod.rs

@@ -372,14 +372,14 @@ impl UncheckedProposal {
     /// Call this after checking downstream.
     pub fn check_broadcast_suitability(
         self,
-        min_feerate: Option<FeeRate>,
+        min_fee_rate: Option<FeeRate>,
         can_broadcast: impl Fn(&bitcoin::Transaction) -> Result<bool, Error>,
     ) -> Result<MaybeInputsOwned, Error> {
         let original_psbt_fee_rate = self.psbt_fee_rate()?;
-        if let Some(min_feerate) = min_feerate {
-            if original_psbt_fee_rate < min_feerate {
+        if let Some(min_fee_rate) = min_fee_rate {
+            if original_psbt_fee_rate < min_fee_rate {
                 return Err(Error::BadRequest(
-                    InternalRequestError::PsbtBelowFeeRate(original_psbt_fee_rate, min_feerate)
+                    InternalRequestError::PsbtBelowFeeRate(original_psbt_fee_rate, min_fee_rate)
                         .into(),
                 ));
             }
@@ -862,9 +862,7 @@ mod test {
         }
     }
 
-    fn proposal_from_test_vector(
-        min_feerate: Option<u64>,
-    ) -> Result<UncheckedProposal, RequestError> {
+    fn proposal_from_test_vector() -> Result<UncheckedProposal, RequestError> {
         // OriginalPSBT Test Vector from BIP
         // | InputScriptType | Orginal PSBT Fee rate | maxadditionalfeecontribution | additionalfeeoutputindex|
         // |-----------------|-----------------------|------------------------------|-------------------------|
@@ -873,17 +871,14 @@ mod test {
 
         let body = original_psbt.as_bytes();
         let headers = MockHeaders::new(body.len() as u64);
-        let min_feerate_param = format!("minfeerate={}", min_feerate.unwrap_or(0));
-        let query = format!(
-            "maxadditionalfeecontribution=182&additionalfeeoutputindex=0&{}",
-            min_feerate_param
-        );
+        let query =
+            format!("maxadditionalfeecontribution=182&additionalfeeoutputindex=0&minfeerate=0");
         UncheckedProposal::from_request(body, &query, headers)
     }
 
     #[test]
     fn can_get_proposal_from_request() {
-        let proposal = proposal_from_test_vector(None);
+        let proposal = proposal_from_test_vector();
         assert!(proposal.is_ok(), "OriginalPSBT should be a valid request");
     }
 
@@ -893,7 +888,7 @@ mod test {
 
         use bitcoin::{Address, Network};
 
-        let proposal = proposal_from_test_vector(None).unwrap();
+        let proposal = proposal_from_test_vector().unwrap();
         let mut payjoin = proposal
             .assume_interactive_receiver()
             .check_inputs_not_owned(|_| Ok(false))
@@ -917,7 +912,7 @@ mod test {
 
     #[test]
     fn psbt_fee_rate() {
-        let proposal = proposal_from_test_vector(None).unwrap();
+        let proposal = proposal_from_test_vector().unwrap();
         assert_eq!(proposal.psbt_fee_rate().unwrap().to_sat_per_vb_floor(), 2);
     }
 }