Apply DKG TX handling code to all sign TXs

The existing code was almost entirely applicable. It just needed to be scoped
with an ID. While the handle function is now a bit convoluted, I don't see a
better option.

coordinator/src/tributary/mod.rs

@@ -327,6 +327,13 @@ impl TransactionTrait for Transaction {
 
   fn verify(&self) -> Result<(), TransactionError> {
     // TODO: Augment with checks that the Vecs can be deser'd and are for recognized IDs
+
+    if let Transaction::BatchShare(data) = self {
+      if data.data.len() != 32 {
+        Err(TransactionError::InvalidContent)?;
+      }
+    }
+
     Ok(())
   }
 }