Add Sharepoint support in Android app

[stefan-karg]

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• [X] I have searched existing issues for duplicates
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Summary

Add support for Sharepoint

Motivation

In the business environment, MS Sharepoint is a common platform to store documents / project files. Currently it's not possible to add a vault located in a Sharepoint document library, but only from OneDrive.

Considered Alternatives

None.

Anything else?

No response