Fix query arg in proposal_from_test_vector

    The previous `query` used `?` to separate between pairs while it
    should be `&` as per the `url_fromencoded` crate.

payjoin/src/receive/mod.rs

@@ -841,7 +841,7 @@ mod test {
         }
     }
 
-    fn proposal_from_test_vector() -> Result<UncheckedProposal, RequestError> {
+    fn proposal_from_test_vector(min_feerate: Option<u64>) -> Result<UncheckedProposal, RequestError> {
         // OriginalPSBT Test Vector from BIP
         // | InputScriptType | Orginal PSBT Fee rate | maxadditionalfeecontribution | additionalfeeoutputindex|
         // |-----------------|-----------------------|------------------------------|-------------------------|
@@ -850,16 +850,16 @@ mod test {
 
         let body = original_psbt.as_bytes();
         let headers = MockHeaders::new(body.len() as u64);
-        UncheckedProposal::from_request(
-            body,
-            "?maxadditionalfeecontribution=182?additionalfeeoutputindex=0",
-            headers,
-        )
+        let min_feerate_param = format!("minfeerate={}", min_feerate.unwrap_or(0));
+        let query = format!(
+            "maxadditionalfeecontribution=182&additionalfeeoutputindex=0&{}", min_feerate_param
+        );
+        UncheckedProposal::from_request(body, &query, headers)
     }
 
     #[test]
     fn can_get_proposal_from_request() {
-        let proposal = proposal_from_test_vector();
+        let proposal = proposal_from_test_vector(None);
         assert!(proposal.is_ok(), "OriginalPSBT should be a valid request");
     }
 
@@ -869,7 +869,7 @@ mod test {
 
         use bitcoin::{Address, Network};
 
-        let proposal = proposal_from_test_vector().unwrap();
+        let proposal = proposal_from_test_vector(None).unwrap();
         let mut payjoin = proposal
             .assume_interactive_receiver()
             .check_inputs_not_owned(|_| Ok(false))