Add source metadata from API response to Document metadata

[rozerarenu]

Corresponding PR in langchain: langchain-ai/langchain#21349

• PR title: "community: Add source metadata to bedrock retriever response"

• PR message:

  • Description: Bedrock retrieve API returns extra metadata in the response which is currently not returned in the retriever response
  • Issue: The change adds the metadata from bedrock retrieve API response to the bedrock retriever in a backward compatible way. Renamed metadata to sourceMetadata as metadata term is being used in the Document already. This is in sync with what we are doing in llama-index as well.
  • Dependencies: No

• Add tests and docs:

  1. Added unit tests
  2. Notebook already exists and does not need any change
  3. Updated and ran integration tests
  4. Response from end to end testing, just to ensure backward compatibility: [Document(page_content='Exoplanets.', metadata={'location': {'s3Location': {'uri': 's3://bucket/file_name.txt'}, 'type': 'S3'}, 'score': 0.46886647, 'source_metadata': {'x-amz-bedrock-kb-source-uri': 's3://bucket/file_name.txt', 'tag': 'space', 'team': 'Nasa', 'year': 1946.0}})]

• Lint and test: Run make format, make lint and make test from the root of the package(s) you've modified. See contribution guidelines for more: https://python.langchain.com/docs/contributing/