fix(cdk): Improve HTTP 400 error message (AI-Triage PR)

[devin-ai-integration]

fix(cdk): Improve HTTP 400 error message (AI-Triage PR)

Summary

Improves the default HTTP 400 error message in DEFAULT_ERROR_MAPPING to comply with Airbyte's error message guidelines.

Before: "HTTP Status Code: 400. Error: Bad request. Please check your request parameters."
After: "Bad request response from source API."

The old message violated several guidelines:

• Contained remediation language ("Please check your request parameters")
• Included redundant implementation detail ("HTTP Status Code: 400")
• Was vague and not actionable for users

The new message is concise, deterministic, and follows the <Subject> <violated_condition> [qualifier]. format.

This change affects all HTTP-based source connectors that rely on the CDK's default error mapping for 400 responses. Connectors with custom error handlers are unaffected.

Related to https://github.com/airbytehq/airbyte-internal-issues/issues/15970

Review & Testing Checklist for Human

• Cross-repo string references: Verify that no connectors or tests in airbytehq/airbyte or other repos assert on the exact old string "HTTP Status Code: 400. Error: Bad request. Please check your request parameters.". A grep across the monorepo is recommended.
• Message wording: Confirm the new message "Bad request response from source API." is clear and appropriate as a generic default for all source connectors encountering HTTP 400.
• FailureType classification: The system_error type is preserved. Consider whether this is the best default for 400 responses (which can indicate either a connector bug or a user config issue depending on context).

Notes

• Prior art: airbytehq/airbyte-python-cdk#918 by Patrick Nilan (@pnilan) proposed a broader overhaul of all HTTP error messages but was closed with CI failures. This PR takes a focused approach, changing only the 400 message that was specifically called out in the tracking issue.
• The FailureType and ResponseAction are intentionally left unchanged to keep this PR minimal and low-risk.

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Requested by: bot_apk
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# Run the CLI from this branch:
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[github-actions]

PyTest Results (Fast)

3 892 tests  ±0   3 880 ✅ ±0   6m 52s ⏱️ +6s
    1 suites ±0      12 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 477787d. ± Comparison against base commit f550424.

This pull request removes 1 and adds 1 tests. Note that renamed tests count towards both.

unit_tests.sources.declarative.requesters.error_handlers.test_default_error_handler ‑ test_default_error_handler_with_custom_response_filter[_with_http_response_status_400_fail_with_default_failure_type-400-test_response_filter0-ResponseAction.RETRY-FailureType.system_error-HTTP Status Code: 400. Error: Bad request. Please check your request parameters.]

unit_tests.sources.declarative.requesters.error_handlers.test_default_error_handler ‑ test_default_error_handler_with_custom_response_filter[_with_http_response_status_400_fail_with_default_failure_type-400-test_response_filter0-ResponseAction.RETRY-FailureType.system_error-Bad request response from source API.]

[github-actions]

PyTest Results (Full)

3 895 tests  ±0   3 883 ✅ ±0   11m 33s ⏱️ +19s
    1 suites ±0      12 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 477787d. ± Comparison against base commit f550424.

This pull request removes 1 and adds 1 tests. Note that renamed tests count towards both.

unit_tests.sources.declarative.requesters.error_handlers.test_default_error_handler ‑ test_default_error_handler_with_custom_response_filter[_with_http_response_status_400_fail_with_default_failure_type-400-test_response_filter0-ResponseAction.RETRY-FailureType.system_error-HTTP Status Code: 400. Error: Bad request. Please check your request parameters.]

unit_tests.sources.declarative.requesters.error_handlers.test_default_error_handler ‑ test_default_error_handler_with_custom_response_filter[_with_http_response_status_400_fail_with_default_failure_type-400-test_response_filter0-ResponseAction.RETRY-FailureType.system_error-Bad request response from source API.]