fix(wot): cannot certify self

An identity should not be able to certify itself.

@librelois

pallets/certification/src/lib.rs

@@ -276,6 +276,8 @@ pub mod pallet {
         NotRespectRenewablePeriod,
         /// This identity has already issued a certification too recently
         NotRespectCertPeriod,
+        /// An identity cannot certify itself
+        CannotCertifySelf,
     }
 
     #[pallet::hooks]
@@ -342,6 +344,9 @@ pub mod pallet {
             let issuer = T::IdtyIndexOf::convert(who).ok_or(Error::<T, I>::IssuerNotFound)?;
             let receiver =
                 T::IdtyIndexOf::convert(receiver).ok_or(Error::<T, I>::ReceiverNotFound)?;
+            if issuer == receiver {
+                return Err(Error::<T, I>::CannotCertifySelf.into());
+            }
             if !T::IsCertAllowed::is_cert_allowed(issuer, receiver) {
                 return Err(Error::<T, I>::CertNotAllowed.into());
             }