Add Delta Lake / Apache Spark Support

[rodobarcaaa]

Extend to support Delta Lake (Databricks, Apache Spark) by using pyspark and delta-spark to connect to tables stored in Delta format.

Why:
Delta Lake is increasingly used in lakehouse architectures. Supporting it expands the utility of nlp2sql to modern data platforms, including Databricks, EMR, and Spark clusters.

Tasks:

• Add DELTA to DatabaseType enum

• Create delta_adapter.py to

  • Initialize SparkSession
  • Extract schema via SHOW TABLES and DESCRIBE TABLE
  • Support schema filtering (schemas = databases in Spark)

• Add optional support for delta-spark dependency

• Extend CLI for --database-type delta

• Update README and usage examples