Use WebDAV library

[stokito]

There are some existing libraries for Android with WebDAv support: https://github.com/WebDAVDevs/awesome-webdav/tree/main?tab=readme-ov-file#java

It would be really great if you can reuse or contribute to this libraries. This will make it easier to support many servers with their quirks and also avoid known bugs. But what is more important is that it will make other app creators easier to add the WebDAV support.

Some libraies:

• https://github.com/thegrizzlylabs/sardine-android based on OkHttp. I'm not sure who using it and also it has a lot of open PRs without traction.
• https://github.com/bitfireAT/dav4jvm from DavX5. This is a very popular program for Calendar syncing but not sure if it works with files.
• https://github.com/McDjuady/dav4jvm fork of the dav4jvm rewritten in Kotlin

I don't know what the NextCloud app uses itself but the owbCloud has a separate lib https://github.com/owncloud/android-library