[Feature] Async generation

[maelanleborgne]

Closes #46

Gotenberg allows async generation of files by passing webhooks urls in dedicated headers. Doing this, the request to Gotenberg server returns a 204 immediately, and once the file is generated, a call will be made by Gotenberg server on the specified endpoint to upload the generated file. This PR aims at enabling easy integration of this feature with the bundle.

The base of the feature is a new interface AsyncBuilderInterface that defines a generateAsync method. The AbstractPdfBuilder and AbstractScreenshotBuilder now implement this interface.
Another important addition is the webhookUrls(string $successWebhook, string|null $errorWebhook) that allows directly setting the webhooks url to use with the builders.

To make things easier when not working directly with urls (if you'd like to generate the url from a route, or if using the Webhook component), a some new configuration options are available :

# packages/sensiolabs_gotenberg.yaml

sensiolabs_gotenberg:  
    # ...
    webhook:  
        # Here you can define any number of webhook configuration so that you can reuse them in builder configs or to switch configuration at runtime
        my_config_name:  
            success:  
                url: 'http://example.com/webhook'
                # route: ['my_route_name', ['param1', 'param2']]
            # This "error" entry is optional. If not set, the "success" configuration will be used for both success and error.
            error:  
                url: 'http://example.com/webhook-error'
                # route: ['my_route_name', ['param1', 'param2']]
    default_options:
        # Here you can define which webhook config to use by default
        webhook: 'my_config_name'
        pdf:
            html:
                webhook: 'my_config_name'
                # Or you can define a specific configuration directly from here
                # webhook:
                #    success:
                #	    url: 'http://example.com/custom-webhook'
    #...

TODO:

• Write documentation
• Add example config to flex recipe
• Change icon in profiler
• Add default webhook configuration in profiler
• Add/fix tests

[Neirda24]

After discussing this with @ConstantBqt we have another usecase to take into account : If we generate the PDF but the webhook is not setup in our own app but is external. We should be able to declare such case. WDYT @maelanleborgne ?

[maelanleborgne]

After discussing this with @ConstantBqt we have another usecase to take into account : If we generate the PDF but the webhook is not setup in our own app but is external. We should be able to declare such case. WDYT @maelanleborgne ?

This is already present in the PR :

// ...
$this->gotenberg->html()
  ->webhookUrls('https://external.service/webhook', 'https://external.service/webhook-error')
  ->webhookExtraHeaders(['X-ExternalService-Secret' => 'a_secret'])
  ->generateAsync()
;

or via the configuration :

sensiolabs_gotenberg:  
    # ...
    webhook:  
        external_service:  
            success:  
                url: 'https://external.service/webhook'
            error:  
                url: 'https://external.service/webhook-error'
    default_options:
        pdf:
            html:
                webhook: 'external_service'

Or maybe I'm missing the point.

[Jean-Beru]

This is already present in the PR :

Could this part be done in a dedicated PR ?

• allow defining a webhook to add as a header
• make "internal" webhook easier to developer using the component

[Jean-Beru]

Quick review