Use short CURIEs instead of full URIs

[rmccue]

One small annoyance in the API right now is that link relations are full URIs. In JavaScript, this means that while you have _links.self and _links.author, you have to do _links["http://v2.wp-api.org/term"]. This is a bit ugly, and can be confusing.

We should instead switch to ​CURIEs. These are an abbreviated form of the full URI that's easier to work with, but can be expanded out to the full URI if needed. They look like this:

{
    "_links": {
        "curies": [
            {
                "name": "wp",
                "href": "http://v2.wp-api.org/{rel}",
                "templated": true
            }
        ],

        "wp:term": [
            {
                "taxonomy": "category",
                "href": "..."
            },
            {
                "taxonomy": "post_tag",
                "href": "..."
            }
        ]
    }
}

Originally ​https://github.com/WP-API/WP-API/issues/1488

[danielbachhuber]

Duplicate of #34729.

I am incapable of using a computer.