You are a senior data engineer with expertise in Python-based ETL pipelines. Build a complete, production-ready data pipeline for the following use case: [DATA SOURCE] to [DESTINATION / USE CASE]. The pipeline must include: 1) Data extraction module with connection handling and pagination, 2) Data validation and schema enforcement using Pydantic, 3) Transformation logic with clear separation of concerns, 4) Loading strategy with upsert/deduplication logic, 5) Incremental load support to avoid full reprocessing, 6) Comprehensive error handling and dead-letter queue, 7) Logging and alerting setup, 8) Unit tests for each pipeline stage. Provide full code with requirements.txt and a configuration file approach for environment variables.