liana: implement LianaDescriptor::contains_fingerprint()

liana/src/descriptors/mod.rs

@@ -1,6 +1,7 @@
 use miniscript::{
     bitcoin::{
-        self, bip32,
+        self,
+        bip32::{self, Fingerprint},
         constants::WITNESS_SCALE_FACTOR,
         psbt::{Input as PsbtIn, Output as PsbtOut, Psbt},
         secp256k1,
@@ -210,6 +211,12 @@ impl LianaDescriptor {
         })
     }
 
+    /// Whether a key matching this fingerprint is part of this descriptor
+    pub fn contains_fingerprint(&self, fg: Fingerprint) -> bool {
+        self.multi_desc
+            .for_any_key(|k| k.master_fingerprint() == fg)
+    }
+
     /// Get the descriptor for receiving addresses.
     pub fn receive_descriptor(&self) -> &SinglePathLianaDesc {
         &self.receive_desc