Extract WebdavFs logic to integrations

[Xuanwo]

Hi, @Young-Flash, do you think it's a good idea to split the impl WebdavFs for opendal logic out to integrations? We can maintain a new crate called dav-server-fs-opendal.

After this change, our depends will become: oay -> dav-server-fs-opendal -> dav-server & opendal.

Benefits:

• Make oay a thin wrapper bin instead of bunch of logic here.
• Easier to test for dav related logic.
• dav-server ecosystem could use dav-server-fs-opendal on their own needs.
• In the future, we can have dav-server-lock-opendal.

Also cc dav-server's maintainer @messense for ideas.

[Young-Flash]

agree. where will the new crate be? a personal repo or under a organization?

[Xuanwo]

Under integrations/dav-server.

[Young-Flash]

Or it is also possible to make WebdavFs directly to dav-server? But it depends on what @messense thinks

[Xuanwo]

I have a discussion with @messense at messense/dav-server-rs#20. We can contribe to upstream once we are stable enough.