create redact util + langchain altn. implementation

[aadityare]

No description provided.

[aadityare]

Will update with better PR description + LangChain test results

[aadityare]

Completed LangChain code with CLI implementation.
To-Do:

• Write LangChain Tests
• Integrate Sanitization Script

[enjhnsn2]

Per the meeting today, I would just keep this PR as a draft, then create a new PR with the "first step" to getting this functionality (the redact util I guess) implemented. Aim for <= 500 loc, which is about the upper bound on what I'm willing to read in a single PR.