transaction: drop Issue TX support

pkg/core/mempool/mem_pool.go

@@ -353,17 +353,6 @@ func (mp *Pool) checkTxConflicts(tx *transaction.Transaction, fee Feer) bool {
 	if !mp.checkBalanceAndUpdate(tx, fee) {
 		return false
 	}
-	switch tx.Type {
-	case transaction.IssueType:
-		// It's a hack, because technically we could check for
-		// available asset amount, but these transactions are so rare
-		// that no one really cares about this restriction.
-		for i := range mp.verifiedTxes {
-			if mp.verifiedTxes[i].txn.Type == transaction.IssueType {
-				return false
-			}
-		}
-	}
 	return true
 }
 

pkg/core/mempool/mem_pool_test.go

@@ -129,29 +129,6 @@ func TestMemPoolVerifyInputs(t *testing.T) {
 	require.Error(t, mp.Add(tx3, &FeerStub{}))
 }
 
-func TestMemPoolVerifyIssue(t *testing.T) {
-	mp := NewMemPool(50)
-	tx1 := newIssueTX()
-	require.Equal(t, true, mp.Verify(tx1, &FeerStub{}))
-	require.NoError(t, mp.Add(tx1, &FeerStub{}))
-
-	tx2 := newIssueTX()
-	require.Equal(t, false, mp.Verify(tx2, &FeerStub{}))
-	require.Error(t, mp.Add(tx2, &FeerStub{}))
-}
-
-func newIssueTX() *transaction.Transaction {
-	tx := transaction.NewIssueTX()
-	tx.Outputs = []transaction.Output{
-		{
-			AssetID:    random.Uint256(),
-			Amount:     util.Fixed8FromInt64(42),
-			ScriptHash: random.Uint160(),
-		},
-	}
-	return tx
-}
-
 func TestOverCapacity(t *testing.T) {
 	var fs = &FeerStub{lowPriority: true}
 	const mempoolSize = 10