[SDK-4141] Add support for Pushed Authorization Requests

[evansims]

Description

This PR adds support for Pushed Authorization Requests (PAR).

Auth0\SDK\Configuration\SdkConfiguration changes:

• A new configuration option, pushAuthorizationRequest (bool type; defaults to false) toggles PAR use.

Auth0\SDK\API\Authentication\PushedAuthorizationRequest has been added, with two methods:

• post() builds and sends a PAR request — POST /oauth/par.
• create() calls post() to send a PAR request, and then builds and returns a /authorize link for the new PAR request.

Auth0\SDK\API\Authentication changes:

• pushedAuthorizationRequest() convenience method has been added, returning an instance of Auth0\SDK\API\Authentication\PushedAuthorizationRequest.

Auth0\SDK\Auth0 changes:

• login() has been updated to support PAR.

Auth0\SDK\Exception\Authentication\ParResponseException added:

• This exception type is raised exclusively when a PAR request fails due to an unexpected response structure.

Testing and Documentation changes:

• New unit tests have been added to cover the changes.
• A new example application, examples/features/authentication/pushed-authorization-request has been added to demonstrate the feature.

Example usage:

<?php

$configuration = new SdkConfiguration(
  pushedAuthorizationRequest: true,
  // ...
);

$sdk = new Auth0($configuration);

$sdk->login();

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (0ccecdf) 100.00% compared to head (2ee277e) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #714 +/- ## =========================================== Coverage 100.00% 100.00% - Complexity 1299 1311 +12 =========================================== Files 61 62 +1 Lines 4537 4587 +50 =========================================== + Hits 4537 4587 +50 ``` | Flag | Coverage Δ | | |---|---|---| | unittests | `100.00% <100.00%> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0#carryforward-flags-in-the-pull-request-comment) to find out more. | [Impacted Files](https://codecov.io/gh/auth0/auth0-PHP/pull/714?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0) | Coverage Δ | | |---|---|---| | [src/API/Authentication.php](https://codecov.io/gh/auth0/auth0-PHP/pull/714?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0#diff-c3JjL0FQSS9BdXRoZW50aWNhdGlvbi5waHA=) | `100.00% <100.00%> (ø)` | | | [.../API/Authentication/PushedAuthorizationRequest.php](https://codecov.io/gh/auth0/auth0-PHP/pull/714?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0#diff-c3JjL0FQSS9BdXRoZW50aWNhdGlvbi9QdXNoZWRBdXRob3JpemF0aW9uUmVxdWVzdC5waHA=) | `100.00% <100.00%> (ø)` | | | [src/Auth0.php](https://codecov.io/gh/auth0/auth0-PHP/pull/714?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0#diff-c3JjL0F1dGgwLnBocA==) | `100.00% <100.00%> (ø)` | | | [src/Configuration/SdkConfiguration.php](https://codecov.io/gh/auth0/auth0-PHP/pull/714?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0#diff-c3JjL0NvbmZpZ3VyYXRpb24vU2RrQ29uZmlndXJhdGlvbi5waHA=) | `100.00% <100.00%> (ø)` | |

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.

[evansims]

Thanks for the review @Widcket, I've pushed some changes based on your feedback