feat: Implement retry mechanism for transient API failures

[danieyal]

This pull request introduces a robust retry mechanism for transient API and network errors in both the legacy and REST clients, improving reliability when communicating with the myTNB APIs. The main changes include a new with_retry helper with exponential backoff, integration of this helper into client methods, and comprehensive tests to ensure correct retry behavior.

Retry mechanism implementation:

• Added a new module retry.py implementing with_retry, a bounded retry helper with exponential backoff for transient HTTP status codes (e.g., 404, 5xx) and network errors, and defined RETRYABLE_STATUS_CODES.
• Updated the APIError exception to include a retryable flag, allowing errors to signal if they should be retried.

Integration into client code:

• Refactored both legacy.py and rest.py clients to wrap API calls with with_retry, raising retryable APIError on transient status codes and ensuring only safe errors are retried. [1] [2] [3] [4] [5] [6] [7]

Testing and validation:

• Added unit tests in test_retry.py to verify the retry logic, including correct handling of retryable and non-retryable errors and network exceptions.
• Extended test_client.py with tests for legacy client retry behavior on transient and persistent 404 errors, and adjusted imports for the new retry constants. [1] [2]

These changes collectively improve the resilience of the client against intermittent backend failures, ensuring transient issues do not unnecessarily surface as hard errors to the caller.

[Copilot]

Pull request overview

This PR adds a bounded retry helper with exponential backoff for transient transport/API failures and integrates it into the legacy and REST transports, with a small extension to APIError to mark errors as retryable.

Changes:

• Introduces mytnb.client.retry.with_retry() plus RETRYABLE_STATUS_CODES and defaults for attempts/delay.
• Extends APIError with a retryable flag and uses it to drive retry decisions.
• Wraps legacy and REST transport requests with the retry helper and adds/extends tests for retry behavior.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/mytnb/client/retry.py	New retry helper with exponential backoff + retryability rules.
src/mytnb/exceptions.py	Adds retryable flag to APIError to support retry signaling.
src/mytnb/client/legacy.py	Wraps legacy ASMX calls with with_retry and marks transient HTTP statuses retryable.
src/mytnb/client/rest.py	Wraps REST GET/POST with with_retry and converts retryable statuses into retryable APIError.
tests/test_retry.py	New unit tests validating retry helper behavior and constants.
tests/test_client.py	Adds legacy-transport retry tests and imports retry defaults.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.