PHP 8.4: Implicitly nullable parameter declarations deprecated

Problem/Motivation

PHP 8.4 deprecates implicitly nullable parameter types. On PHP 8.4+ the following deprecation is triggered:

Deprecated function: Drupal\social_api\AuthManager\OAuth2Manager::__construct(): Implicitly marking parameter $request as nullable is deprecated, the explicit nullable type must be used instead in include()

Steps to reproduce

1. Run a site with Social API enabled on PHP 8.4 or later.
2. Load any page that instantiates an OAuth2 manager (e.g. a Social Auth login route).
3. See the deprecation message in the log or on screen.

Proposed resolution

Use explicit nullable types, e.g. in src/AuthManager/OAuth2Manager.php:

- Request $request = NULL
+ ?Request $request = NULL

Check the rest of the module for the same pattern and fix all occurrences. Explicit nullable types are supported since PHP 7.1, so there are no backwards-compatibility concerns.

Remaining tasks

• Create MR
• Review

User interface changes

None.

API changes

None.

Data model changes

None.