Handle the combination of DKG removals with re-attempts

With a DKG removal comes a reduction in the amount of participants which was
ignored by re-attempts.

Now, we determine n/i based on the parties removed, and deterministically
obtain the context of who was removd.

coordinator/tributary/src/block.rs

@@ -249,8 +249,6 @@ impl<T: TransactionTrait> Block<T> {
       }
       last_tx_order = current_tx_order;
 
-      // TODO: should we modify the verify_transaction to take `Transaction<T>` or
-      // use this pattern of verifying tendermint Txs and app txs differently?
       match tx {
         Transaction::Tendermint(tx) => {
           match verify_tendermint_tx::<N>(tx, schema.clone(), &commit) {

coordinator/tributary/src/blockchain.rs

@@ -272,6 +272,7 @@ impl<D: Db, T: TransactionTrait> Blockchain<D, T> {
       provided_in_chain,
       allow_non_local_provided,
     );
+    // Drop this TXN's changes as we're solely verifying the block
     drop(txn);
     res
   }

coordinator/tributary/src/transaction.rs

@@ -179,7 +179,6 @@ pub trait Transaction: 'static + Send + Sync + Clone + Eq + Debug + ReadWrite {
 pub trait GAIN: FnMut(&<Ristretto as Ciphersuite>::G, &[u8]) -> Option<u32> {}
 impl<F: FnMut(&<Ristretto as Ciphersuite>::G, &[u8]) -> Option<u32>> GAIN for F {}
 
-// This will only cause mutations when the transaction is valid
 pub(crate) fn verify_transaction<F: GAIN, T: Transaction>(
   tx: &T,
   genesis: [u8; 32],
@@ -204,7 +203,7 @@ pub(crate) fn verify_transaction<F: GAIN, T: Transaction>(
         Err(TransactionError::InvalidSigner)?;
       }
 
-      // TODO: Use Schnorr half-aggregation and a batch verification here
+      // TODO: Use a batch verification here
       if !signature.verify(*signer, tx.sig_hash(genesis)) {
         Err(TransactionError::InvalidSignature)?;
       }