feat: add support for Path & DocumentStream

[ehcalabres]

Background

While using DocumentLoader with LangChain, I noticed that although pathlib.Path and docling.datamodel.base_models.DocumentStream are supported input types in Docling, the loader here only accepted a string (representing either a file path or URL). This limitation made the integration less flexible and somewhat inconvenient.

Changes

This PR adds support for both DocumentStream and pathlib.Path as input types, allowing docling-langchain to align more closely with the Docling API for document loading.

Breaking Changes

To reflect this input change, the file_path parameter has been renamed to source, consistent with the naming used in the Docling converter interface.

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[mergify]

Merge Protections

Your pull request matches the following merge protections and will not be merged until they are valid.

🔴 Require two reviewer for test updates

This rule is failing.

When test data is updated, we require two reviewers

• #approved-reviews-by >= 2

🟢 Enforce conventional commit

Wonderful, this rule succeeded.

Make sure that we follow https://www.conventionalcommits.org/en/v1.0.0/

• title ~= ^(fix|feat|docs|style|refactor|perf|test|build|ci|chore|revert)(?:\(.+\))?(!)?: