Update for Shrine 3.0

[janko]

In Shrine 2.x we've already stopped using the #download storage method (see shrinerb/shrine#331 for the rationale). So we can remove it here. The google client should already be doing resumable downloads in the #open method as well, so we shouldn't be losing anything by switching to #open.

Shrine 3.0 now requires the #open method to accept optional keyword arguments. We add the :rewindable option to allow people to disable Down::ChunkedIO's disk caching, which has become a convention across Shrine storages. We also forward any additional options Google::Cloud::Storage::File#download, to give people more control over downloading should they want it.

Lastly, we relax the shrine version constraint to allow Shrine 3.x. Shrine 3.0 isn't officially released yet, but we already have a beta that seems pretty stable, and we'll soon be releasing a RC, so it would be nice if people can already test with GCS.

[janko]

I also remembered the Shrine 3.0 requires #open to raise Shrine::FileNotFound on missing file. I'm not sure to how detect it properly, so I was hoping to get some help from you, I added some placeholder code.

I initially wanted to still keep allowing Shrine 2.x, but the new Shrine::FileNotFound exception doesn't exist in 2.x, so I bumped the shrine version specifier to >= 3.x.

[renchap]

Thanks @janko!
I am currently on vacation, I will review this and test my app with Shrine 3 once I am back (after the 7th of october). Feel free to ping me if I forget :)

[steveclarke]

Any update on merging this request? I'm ready to upgrade to Shrine 3.0 and this is a blocker. Much appreciated!

[renchap]

Thanks @janko!
This will go in the 3.0.0 release of this gem, as this is a breaking change. I will publish it soon.

[janko]

Thanks! Just a reminder that this PR was still missing detecting unknown file in #open.

[renchap]

Woops sorry, I missed this and I was minutes away from releasing the new version. I will have a look then :)

[renchap]

I just opened #40 for this.

[renchap]

Shrine 3.0 compatibility has just been released in version 3.0.0 🎉