Optional parameter $upload declared before required parameter $contents is implicitly treated as a required parameter

[piridium]

Bug Report

Current Behavior
Update fof/upload from 1.5.8 to 1.6.0 throws the following deprectation error:

Deprecated: Optional parameter $upload declared before required parameter $contents is implicitly treated as a required parameter in ./vendor/fof/upload/src/Adapters/Flysystem.php on line 55

Environment

• Flarum version: 1.8.9
• Extension version: ^1.6.0
• Webserver: apache
• Hosting environment: local development server
• PHP version: 8.2.25

Possible solution(s)
Switching off deprecation warnings is not a good idea because
a) I want to have them enabled on the dev server, and
b) we should fix deprecations in order to not run into any problems in the future.

As of php 8.0 having an optional parameter followed by a required one is deprecated. (https://www.php.net/manual/en/migration80.deprecated.php)
It is recommended to use a explicit nullable type instead.

Suggestion:

# change line 55 from
public function upload(File $file, ?UploadedFile $upload = null, $contents)
# into
public function upload(File $file, ?UploadedFile $upload, $contents)

This gets rid of the error. And as UploadedFile is explicitly nullable, it should be ok, right? This is where I am not sure if we will run into any problems if a caller does not specify UploadedFile.

Additional Context
Duplicate of #407 which has already been closed.

[piridium]

This is still preventing us from upgrading to 1.6.0+. How is everybody else doing it? Did you guys all deactivate deprecation warnings?!