Add support for files API endpoints

[mattt]

In #198, we added support for automatically encoding binary prediction inputs as base64-encoded data URIs.

This PR adds support for the new (write-only) files API. By default, each binary input is uploaded and replaced with a URL to the created file. Before the inputs are sent to the model to be run, Replicate's API rewrites the URL to make the file downloadable.

From the perspective of the caller, the out-of-the-box experience is the same: You pass a file handle or blog as an input, and that's it — everything just works. And with the files API, things work much better for larger files, whose data URI encoding can cause write timeouts and other problems.

What I'm less clear about is how to customize this behavior. My current solution is two-fold:

• Add a prepareInputs property to the client
• Export the transformFileInputsToBase64EncodedDataURIs and transformFileInputsToReplicateFileURLs helper functions

By default, prepareInputs tries to upload files and falls back to data URI encoding (for example if the files API is unavailable for some reason).

this.prepareInputs =
  options.prepareInputs ||
  (async (inputs) => {
    try {
      return await transformFileInputsToReplicateFileURLs(this, inputs);
    } catch (error) {
      return await transformFileInputsToBase64EncodedDataURIs(inputs);
    }
  });

Users can override this to customize the behavior however they like. For example, they could only base64-encode inputs, conditionalize based on file size / content, or throw an error.

I'm pretty sure we need it to be this flexible. But is it too clunky? Would love to hear your thoughts, @aron @zeke.

[zeke]

Nice! I may not be the right power-user customer to ask about that prepareInputs API but it looks sensible to me. 👍🏼

Needs docs.

Just came across @aron's #198 which already updated the README to use this glamorous snippet:

const input = {
  image: await fs.readFile("path/to/image.png"),
};

[aron]

Exciting!!!

Some late night thoughts, I think prepareInputs needs a second pass. And I do think we should consider the surface area of the files api but otherwise I am so excited to get this in.

[aron]

@mattt I've incorporated the feedback, updated the code to use a FileUploadStrategy option which can consist of "default" | "upload" | "data-uri".

Types have been updated and the tests now verify the FormData body, this was a bit fiddly because nock doesn't support it natively so I had to spy on fetch() too.

[aron]

@mattt I've removed the replicate.files API for the moment from the client. I think this is a good first step to improve our file input support.

[zeke]

Rebased and fixed merge conflicts. Anything blocking this from shipping?

[zeke]

@mattt bump