feat: add delete_all_documents() to MongoDB DocumentStore

[ChinmayBansal]

Related Issues

• fixes add delete_all_documents() operation to MongoDBDocumentStore #2314

Proposed Changes:

Added delete_all_documents() and delete_all_documents_async() methods to MongoDBAtlasDocumentStore to enable deletion of all documents from a collection.

Implementation details:

• Both sync and async versions implemented following the existing delete_documents() pattern
• Uses MongoDB's native delete_many({}) command with an empty filter to efficiently delete all documents
• Follows established patterns from other document stores (Elasticsearch, OpenSearch, Weaviate)
• Simple implementation without recreate_index parameter (not needed for MongoDB's schema-flexible collections)

Files changed:

• document_store.py: Added both methods
• test_document_store.py: Added 2 sync integration tests
• test_document_store_async.py: Added 2 async integration tests

How did you test it?

• ✅ Linter: hatch run fmt - All checks passed (15 files unchanged)
• ✅ Type checks: hatch run test:types - No issues found
• ✅ Unit tests: hatch run test:unit - 25 passed
• ✅ Integration tests: Added 4 new integration tests (2 sync + 2 async):
  • test_delete_all_documents: Verifies deletion of multiple documents
  • test_delete_all_documents_empty_collection: Verifies behavior with empty collection
  • test_delete_all_documents_async: Async version with multiple documents
  • test_delete_all_documents_async_empty_collection: Async version with empty collection

Notes for the reviewer

• The implementation is intentionally simpler than Elasticsearch/OpenSearch/Weaviate versions - MongoDB doesn't require index recreation or batch deletion for this operation
• Follows the exact same pattern as the existing delete_documents() method in the same file for consistency
• No error handling wrapper added to match the existing delete_documents() implementation style

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.