Better handle errors

[jm-rivera]

This pull request improves the robustness of the dataflow version fallback logic in the ODA Reader package. The main enhancement is that API error detection now checks the response content for error patterns, regardless of HTTP status code, allowing for more reliable handling of cases where error messages are returned with non-404 status codes.

Dataflow version fallback robustness:

• Added the _is_dataflow_not_found_error function to detect dataflow/version not found errors in API responses by matching known error patterns and checking for invalid CSV responses. (src/oda_reader/common.py)
• Updated the version fallback logic in get_data_from_api to use _is_dataflow_not_found_error for error detection, triggering retries regardless of HTTP status code and improving error message reporting after maximum retries. (src/oda_reader/common.py)

Release and metadata updates:

• Bumped the package version to 1.3.4 in pyproject.toml to reflect the new changes. (pyproject.toml)
• Documented the improved dataflow fallback logic in the changelog for version 1.3.4. (CHANGELOG.md)