apply codes to php8.4（PHP8.4にコードを対応させる）

[77web]

Do this before creating an issue

• ✅ Check our developer documentation and FAQ page for more information on LINE bots and the Messaging API
• ✅ Make sure your issue is related to the LINE Bot SDK. For general questions or issues about LINE bots, create an issue on the LINE Platform feedback repository. Note that we don't provide technical support.

When creating an issue

We want to update our product to php8.4. In php8.4 environment almost every model object has this problem:

Implicitly marking parameter $data as nullable is deprecated, the explicit nullable type must be used instead

In php8.4, the nullable value should be marked as nullable explicitly.
refs. https://www.php.net/manual/ja/migration84.deprecated.php

- function foo (array $data = null)
+ function foo (array|null $data = null)

[Yang-33]

Hi, thank you for using line-bot-sdk-php, @77web !

Here is my question:
Do all the libraries used by your(user) application need to make such adjustments in order for all warnings to disappear? In other words, is this adjustment necessary even for the libraries that the application depends on? Is it not possible to suppress them?

Ultimately, I understand the situation, so we would like to consider a solution. The method is almost singular: to modify the comments generated by the openapi generator based on whether they are nullable. If the openapi generator has not yet addressed this issue and you are interested, you can tackle this problem.

• https://github.com/OpenAPITools/openapi-generator/pulls?q=is%3Apr+PHP

[77web]

I've sent a PullRequest to openapi-generator.
OpenAPITools/openapi-generator#20243

[77web]

My PullRequest to openapi-generator was successfully merged!
OpenAPITools/openapi-generator#20243

Maybe you can apply to php8.4 in upcoming openapi-generator v7.11.0 😄

[Yang-33]

Thank you, @77web !!!! That is great contribution for all users openapi-generator!

We'll update the library for line-bot-sdk-php after openapi-generator v7.11.0 is released. Let us release new version for line-bot-sdk-php and close this after updating version! Thanks!