CDC_Mortality_UnderlyingCause

[goutamabrol]

Summary

PR checklist - link

Adds the CDC_Mortality_UnderlyingCause import under statvar_imports/us_cdc/county_mortality/ for CDC WONDER county-level mortality data.

Data Source: CDC WONDER Underlying Cause of Death (Database D158), covering all ~3,143 US counties from 2018 to 2024.
Coverage: Maps 118 active StatVars (116 with 2024 data + 2 rare causes with 2023 data) across 137 mapped causes in the ICD-10 113 list.
Downloader (download.py): Automates session agreements, form-based year discovery, query partitioning (75k-row cap), and 31-min silent backoff on HTTP 429.
Mappings: Dynamic 5-digit FIPS zero-padding (geoId/{CountyCode1}) in PV map with no hardcoded county lookup tables.
Automation (manifest.json): Configured for Cloud Batch execution with download.py, stat_var_processor.py, and monthly cron.
Validation (validation_config.json): Enforces 0.1% historical deletion threshold and dynamic date freshness (SQL_VALIDATOR) for standard and rare causes.
Testing: 16/16 unit tests pass locally (download_test.py).

Cloud Batch job (test) - link

Validation - link

CRA Report - link

[gemini-code-assist]

Code Review

This pull request introduces a new automated importer for CDC WONDER County-Level Mortality Data, including a download script, metadata, mapping files, unit tests, and validation configurations. The reviewer feedback highlights two important improvements for the download script: first, making the is_state_downloaded check more robust to ensure all intermediate years are covered rather than just the first and last; second, modifying the downloader to log errors and continue processing other states instead of immediately terminating the script with logging.fatal when a single state fails.