Support additional file types in SharePoint / OneDrive loaders

[MacanPN]

Checked

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Feature request

Currently O365BaseLoader (and consequently both derived loaders) are limited to pdf, doc, docx files. In this PR I'm introducing handlers argument that allows to process any file type with suitable parser implemented. User can also implement custom parser and pass that in. Please like the PR if that's something you'd like to see merged in.

In follow-up PR I also want to introduce a wrapper for DocumentLoaders to be converted into parsers. This is because there are implemented many Document Loaders without any corresponding parser. Such wrapper would open many additional file types to be used here.

Motivation

Sharepoint / Onedrive libraries can contain any type of documents. Being able to process only pdf, doc and docx documents is inadequate. Additionally these loaders currently hard-code the parser to be used. It is crucial to enable user to decide which parser they want to use (only pdf filetype currently has 7 different parser implementations). Allowing user to customize the parser used is also very useful feature.

Proposal (If applicable)

No response