When a query fails and closes the transaction, other queries in the same transaction throw unhelpful errors

[alexjpwalker]

Problem to Solve

When running concurrent queries in a transaction, and one of them fails causing the transaction to close, it's possible to get an unhelpful "Transaction closed" error when fetching answers for the other queries.

Proposed Solution

Solving this properly requires us to implement an improved error protocol:

• Build flexible client-server error architecture to replace gRPC error states typedb#6146)

Additional information

We've previously tried to fix this issue with patches:

• Propagate exceptions throughout transactions #367
• Store error on transaction stream #368

But they resulted in error handling becoming counter-intuitive in the context of a stream or iterator. We ended up reverting these patches.