Add OAS 3.0 support

[zeroimpl]

Any plans to add an OAS 3.0 version?
I tried running Gendarme with the spec from https://github.com/googleapis/gnostic/blob/master/OpenAPIv3/openapi-3.0.json and it didn't quite work - there were a few syntax errors (classes named "2" and "4") and I think a few other quirks.

[calcinai]

Hey, I just had a look at this and seems to be a simple fix. It's just an issue with numeric keys, but because PHP's loose types, it's not handled by default.

I'd say that by testing if the key is all numeric would be enough. Feel free to make a PR, otherwise I'll have a look at it when I get a chance.

[zeroimpl]

Thanks. I had worked around that issue (I think), but it seemed like there were a few other issues as well.

For example, I had been trying to figure out how to set the content of a Response object - in OAS 3.0 it seems for each status code you need to create a map from content type (eg 'application/json') to the actual object. I couldn't figure out how to get the MediaTypes class working for that, which is needed by the setContent method of Response. So I decided to try just initializing an instance from an existing OAS 3.0 spec and dump the PHP object for that, but this failed as well:

$schema = json_decode(file_get_contents('https://raw.githubusercontent.com/googleapis/gnostic/master/examples/v3.0/json/petstore.json'));
$swagger = \Calcinai\Strut3\Swagger::create($schema);
var_export( $swagger );

The above fails with:

PHP Fatal error:  Uncaught exception 'InvalidArgumentException' in Calcinai\Strut3\BaseSchema.php:201
Stack trace:
#0 BaseSchema.php(172): Calcinai\Strut3\BaseSchema::tryToCast(Array, Array)
#1 BaseSchema.php(29): Calcinai\Strut3\BaseSchema->parseData(Array)
#2 BaseSchema.php(219): Calcinai\Strut3\BaseSchema->__construct(Array)
#3 swagger-gen3test.php(53): Calcinai\Strut3\BaseSchema::create(Array)

So at the moment I'll probably stick with doing 2.0 then since it works well enough and I don't have enough time to spend on experimenting with 3.0 right now. Anyways thanks for taking a look at this.

[calcinai]

@zeroimpl did you get a chance to test this? Sorry it took me so long to get working!

[zeroimpl]

@calcinai Taking a look now. Looks like will be quite a few things to tweak to get my code working with the new version.
I did run into one issue so far though - calling setExample('blah') on Schema fails with:

exception 'InvalidArgumentException' with message '[Calcinai\Strut\Definitions\Schema] does not accept property [example]'

I think in Schema.php you need to replace

'example' => ['mixed']

with

'example' => []

There are a few other places with reference to 'mixed' as well.

[calcinai]

Oh man, it's so close! I'll take a look at it soon