fix: Correctly map transactions without counterparty

Before this change, transactions that did not have a counterparty were
not correctly mapped and could not be insterted into Firefly III. That
is not correct: _all_ transactions must be added to Firefly III.

Furthermore, Firefly III already has logic to deal with this, and rules
that can solve it manually as well.

banks2ff/src/adapters/firefly/client.rs

@@ -146,9 +146,7 @@ impl TransactionDestination for FireflyAdapter {
                 None
             },
             source_name: if is_credit {
-                tx.counterparty_name
-                    .clone()
-                    .or(Some("Unknown Sender".to_string()))
+                tx.counterparty_name.clone()
             } else {
                 None
             },
@@ -158,9 +156,7 @@ impl TransactionDestination for FireflyAdapter {
                 None
             },
             destination_name: if !is_credit {
-                tx.counterparty_name
-                    .clone()
-                    .or(Some("Unknown Recipient".to_string()))
+                tx.counterparty_name.clone()
             } else {
                 None
             },

banks2ff/src/adapters/gocardless/mapper.rs

@@ -8,6 +8,7 @@ use std::str::FromStr;
 pub fn map_transaction(tx: Transaction) -> Result<BankTransaction> {
     let internal_id = tx
         .transaction_id
+        .or(tx.internal_transaction_id)
         .ok_or_else(|| anyhow::anyhow!("Transaction ID missing"))?;
 
     let date_str = tx