Reduce the number of macros used for SignedExtensions

Reduce the number of macros used for SignedExtensions

Signed-off-by: Serban Iorga <serban@parity.io>

bridges/primitives/runtime/src/lib.rs

@@ -35,6 +35,7 @@ pub use chain::{
 };
 pub use frame_support::storage::storage_prefix as storage_value_final_key;
 use num_traits::{CheckedSub, One};
+use sp_runtime::transaction_validity::TransactionValidity;
 pub use storage_proof::{
 	Error as StorageProofError, ProofSize as StorageProofSize, StorageProofChecker,
 };
@@ -400,6 +401,12 @@ pub trait OwnedBridgeModule<T: frame_system::Config> {
 	}
 }
 
+/// A trait for querying whether a runtime call is valid.
+pub trait FilterCall<Call> {
+	/// Checks if a runtime call is valid.
+	fn validate(call: &Call) -> TransactionValidity;
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;