Do I need to add some other tests? So far I have tested this with my own program and stat and write work as expected

Do I need to add some other tests? So far I have tested this with my own program and stat and write work as expected

We have integration tests for gcs, so it should fine as is.

I just realized that although I've added support for presign within Gcs service, FuturePresignWrite itself does not have content_encoding function.

I wonder if me adding content_encoding to FuturePresignWrite would be beyond the scope of this simple PR? Adding the following function there doesn't seem too complicated though:

    /// Set the content encoding of the operation
    pub fn content_encoding(self, v: &str) -> Self {
        self.map(|(args, dur)| (args.with_content_encoding(v), dur))
    }

I wonder if me adding content_encoding to FuturePresignWrite would be beyond the scope of this simple PR? Adding the following function there doesn't seem too complicated though:

It's looks fine to me. Feel free to add in this PR directly.

I will add it, but I'm not able to test it, because the Gcs service ACL logic is problematic, and I get an error like this when testing:

<?xml version='1.0' encoding='UTF-8'?>
<Error>
	<Code>InvalidArgument</Code>
	<Message>Invalid argument.</Message>
	<Details>Invalid canned acl: publicRead</Details>
</Error>

It turns out that the XML API predefined ACLs uses kebab casing instead of camel casing, and thus publicRead should be converted to public-read when signing urls.

https://cloud.google.com/storage/docs/access-control/lists#predefined-acl

Okay, I tested presign without predefinedAcl, and now it works. That problem should be addressed in a separate PR.

In my opinion this PR is ready to be merged

Thank you @wlinna for working on this. It's really happy to work with you.

Thanks for making it easy to contribute :)