Add default impl for MinXcmFee::GetByKey

Signed-off-by: Georgi Zlatarev <[email protected]>

traits/src/get_by_key.rs

@@ -1,3 +1,5 @@
+use xcm::v1::MultiLocation;
+
 /// A trait for querying a value by a key.
 pub trait GetByKey<Key, Value> {
 	/// Return the value.
@@ -55,3 +57,11 @@ mod tests {
 		assert_eq!(Test::get(&3), 2);
 	}
 }
+
+// Default implementation for xTokens::MinXcmFee
+pub struct DisabledParachainFee;
+impl GetByKey<MultiLocation, Option<u128>> for DisabledParachainFee {
+    fn get(_key: &MultiLocation) -> Option<u128> {
+        None
+    }
+}