"Body" trait.

[Greg Bowler]

These functions are available on the Response and Request. Can't see when they would be used to obtain the Request body content, but hey...

https://developer.mozilla.org/en-US/docs/Web/API/Body

[Greg Bowler]

Methods to implement:

• arrayBuffer() The ArrayBuffer object is used to represent a generic, fixed-length raw binary data buffer. For our purposes, we will need to return a traversable object, but not sure how much use a fully-fledged ArrayBuffer will be to PHP.
• blob() A Blob object represents a file-like object of immutable, raw data. While a Blob can be seen as a string (file_put_contents($blob)), it has some properties and methods that are useful to implement, such as size and slice()
• formData() The FormData interface provides a way to easily construct a set of key/value pairs representing form fields and their values, which can then be easily sent as another fetch body.
• json() Returns an object literal containing the response data (StdClass?)
• text() Returns the string, formatted in the correct encoding, according to the Encoding header.