Migrate to official Dropbox PHP Core SDK

[LukasReschke]

We need to migrate from the current unofficial and unmaintained Dropbox SDK we use at the moment to the official one: https://www.dropbox.com/developers/core/sdks/php

Test plan:

• use big files and slow networks - refs Dropbox Mount File 50MB Download issue #7821

[PVince81]

Makes sense. I hope it can also help to make update detection more easily and magically improve performance 😉

[DeepDiver1975]

I'd really be happy to take the opportunity to also extract dropbox to it's own app.
In an ideal world moving it to a new repo and distribute the app via the appstore.

[LukasReschke]

@icewind1991 Maybe something for combination with the FlySystem thing we introduce at some Point of Time? (#14551)

[DeepDiver1975]

I dont see this happening .....

[PVince81]

The flysystem base work has made it into code.

With a bit of luck, writing an adapter for Flysystem's Dropbox might be minimal.
See how it's done for FTP: https://github.com/icewind1991/files_external_ftp

[PVince81]

and make sure the library doesn't store the whole file in memory...

Moving to 9.1

[PVince81]

Closing in favor of #25969

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.