test(axelar-gateway): rework auth unit tests to integration tests (#93)

Co-authored-by: Milap Sheth <milap@interoplabs.io>

contracts/axelar-gateway/src/contract.rs

@@ -34,9 +34,7 @@ impl AxelarGateway {
             minimum_rotation_delay,
             previous_signers_retention,
             initial_signers,
-        )?;
-
-        Ok(())
+        )
     }
 }
 
@@ -205,6 +203,14 @@ impl AxelarGatewayInterface for AxelarGateway {
     fn signers_hash_by_epoch(env: &Env, epoch: u64) -> Result<BytesN<32>, ContractError> {
         auth::signers_hash_by_epoch(env, epoch)
     }
+
+    fn validate_proof(
+        env: &Env,
+        data_hash: BytesN<32>,
+        proof: Proof,
+    ) -> Result<bool, ContractError> {
+        auth::validate_proof(env, &data_hash, proof)
+    }
 }
 
 impl AxelarGateway {

contracts/axelar-gateway/src/interface.rs

@@ -33,4 +33,11 @@ pub trait AxelarGatewayInterface:
 
     /// Returns the signers hash by epoch.
     fn signers_hash_by_epoch(env: &Env, epoch: u64) -> Result<BytesN<32>, ContractError>;
+
+    /// Validate the `proof` for `data_hash` created by the signers. Returns a boolean indicating if the proof was created by the latest signers.
+    fn validate_proof(
+        env: &Env,
+        data_hash: BytesN<32>,
+        proof: Proof,
+    ) -> Result<bool, ContractError>;
 }