feat: Add string-based namespace support in Txns

[matthewmcneely]

Description

This PR adds string-based namespace support to the Txn class. Managing transactions manually is something common in many repos that use the dgo client. This new functionality makes upgrading transaction-heavy code (that wants to use string-based namespaces) less cumbersome.

Checklist

• Code compiles correctly and linting passes locally
• For all code changes, an entry added to the CHANGELOG.md file describing and linking to
  this PR
• Tests added for new functionality, or regression tests for bug fixes added as applicable

[Copilot]

Pull Request Overview

This PR adds string‐based namespace support to transactions in the Txn class to simplify manual transaction management with the dgo client.

• Introduces NewTxnInNamespace and NewReadOnlyTxnInNamespace methods in txn.go.
• Adds comprehensive tests in v2_test.go and examples_test.go to verify namespace behavior.
• Updates docker-compose.yml to include non‐ACL service configurations for testing.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
v2_test.go	Adds tests for namespace creation, duplicate namespace error handling, and Txn usage.
txn.go	Introduces new namespace field and helper methods for namespace-aware transactions.
t/docker-compose.yml	Provides new docker services for a non‑ACL environment to support testing.
examples_test.go	Adds functions to obtain dgo clients in non‑ACL mode and tests namespace support.

Comments suppressed due to low confidence (1)

txn.go:67

• Correct the abbreviation 'Tnx' to 'Txn' for clarity in the comment.

// in the default namespace. Note that a Tnx created with this function will not complete successfully as the

[RJKeevil]

I think this would be a great improvement.

With the V2 apis, namespaces are simple and a separate concept from ACL/auth, which is fantastic and exactly what I need. We have some graphs that update continuously, and others that are a monthly dump to be dropped and recreated in full. Namespaces gives me an easy way to acheive this data separation. I do not need different auth rules and user separation across the namespaces, as they are purely used by a single backend service.

The missing parts are to enable namespace selection everywhere, without requiring different logins. So dgo transactions, graphQL admin requests (upload schema etc), graphQL queries and the Ratel/play UI. Happy to add additional info if it helps!

See https://discuss.hypermode.com/t/v25-multitenency/19915/3

[RJKeevil]

Now that I understand that apiv2 currently deprecates json-based mutatations this change is very important, as I can fall back to legacy apis for these, provided I have a way to set namespaces, which this PR provides.