Add integration tests for the Branch development ETL pipeline:
- BranchDevEtlTests with tests for pipeline creation and execution
- Tests verify pipeline creates correctly and loads data from cache files
- Added appsettings.json with local connection string and cache directory
- Added necessary packages (Configuration.Json, SqlClient, Dapper)
Tests require local SQL Server and CACHED_DB_FILES directory with
branch.json.zstd to pass; tests silently skip if resources unavailable.
Joseph Doherty