Replace Async functionality

[g105b]

PHP.Gt/Async and PHP.Gt/Promise will reduce the dependency complexity.

[g105b]

Currently the 1st "basic usage" example works fully, but if it's forced to decode JSON with a syntax error the promise rejection is eaten up silently... investigating next.

[g105b]

This is harder than I thought it would be.

[g105b]

The entire codebase is greatly improved and tidy now, with more type safety, but this issue still remains as the only known bug.

Fetch/src/Response/BodyResponse.php

Lines 113 to 131 in 144cedb

	public function json(int $depth = 512, int $options = 0):Promise {
	$newDeferred = new Deferred();
	$newPromise = $newDeferred->getPromise();
	$deferredPromise = $this->deferred->getPromise();
	$deferredPromise->then(function(string $resolvedValue)
	use($newDeferred, $depth, $options) {
	$builder = new JsonObjectBuilder($depth, $options);
	try {
	$json = $builder->fromJsonString($resolvedValue);
	$newDeferred->resolve($json);
	}
	catch(JsonDecodeException $exception) {
	$newDeferred->reject($exception);
	}
	});
	return $newPromise;
	}

This is where the issue lies, in the resolution of the JSON data. If the JSON data is invalid, like it is when used in example/01-basic-fetch.php, the exception is thrown rather than passed up the promise chain.

It's actually not a breaking issue, because it only represents internal failures (things like curl exceptions, timeouts or when $response->ok fails, are all still caught correctly). It might make sense to release the code in its currently improved state, then track this issue in a separate issue to return to later.