feat: add client factory

[gehrisandro]

This adds the ability to configure the client instance via a new factory:

Excerpt from the updated README.

$yourApiKey = getenv('YOUR_API_KEY');

$client = OpenAI::factory()
    ->withApiKey($yourApiKey)
    ->withOrganization('your-organization') // default: null
    ->withBaseUrl('openai.example.com/v1') // default: api.openai.com/v1
    ->withHttpHeader('X-My-Header', 'foo')
    ->withHttpClient(new \GuzzleHttp\Client([])) // default: HTTP client found using PSR-18 HTTP Client Discovery
    ->make();

This change is breaking as the "guzzlehttp/guzzle" has been removed. Existing projects without an explicitly installed HTTP client have to install the Guzzle Client manually:

composer require guzzlehttp/guzzle

With this change we can resolve various issues:

• Make base URI configurable #30
• #30 Add method to create client with custom base URI #31
• Add Timeout Param #39
• Allows to change the HTTP client in the factory #65
• Add Proxy Support for HTTP Request #67

[gehrisandro]

I am going to fix the failing checks later today...

[gehrisandro]

@GromNaN @nicolas-grekas What do you think? Does this what you need for the symfony integration?

[GromNaN]

What do you think? Does this what you need for the symfony integration?

The factory is useful pattern, but personally I prefer parameters (and named parameters), this is less methods to define and call.

[seebyyu]

@gehrisandro Hello, please adjust it as soon as possible openai-php/laravel