Add support for PostSampleAlternates

[zevaryx]

Reasoning

The API now has a field inside of sample called alternates. This field is usually empty, but is filled when there are different resolution sizes for a sample for videos. See post 2474986 for a rating:s sample. Additionally, with an update between when I first started this patch and now, they added it so every post now has this field (see post 39 for a rating: example of it being applied to an extremely old post).

Solution

An extra struct (PostSampleAlternates) and an extra field (alternates) allow for proper handling of this.

Example usage:

let client = rs621::client::Client::new("https://e926.net", "rs621/0.6.0 (by zevaryx on e621)")?;
let mut post_stream = client.get_posts(&[2474986]);

while let Some(post) = post_stream.next().await {
    let tmp_post = post?;
    print!("Post #{}:", tmp_post.id);
    for key in tmp_post.sample.alternates.keys() {
        print!(" {}", key);
    }
    println!("");
}

[nasso]

Oh my god I just realised I wasn't watching the repository for some reason so I was never notified of your pull request. My bad.

I will take a look as soon as I can!

[zevaryx]

No worries! I actually forgot about this PR, so not a big deal

[nasso]

Do the tests still pass? The fake payloads might have to be updated.

Also please rebase onto master!

[nasso]

It should probably be singular: PostSampleAlternate