chore: Drop unsupported PHP versions and rector to 8.1

[dragonmantank]

Description

Push minimum PHP version to 8.1 and updates code to 8.1 minimum using Rector

Motivation and Context

PHP regularly drops support for older PHP versions and our standard is to stick with only supported PHP versions.

How Has This Been Tested?

Unit tests

Example Output or Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[Copilot]

Pull Request Overview

This PR modernizes the OpenTok PHP SDK codebase by dropping support for unsupported PHP versions and upgrading to PHP 8.1 as the minimum requirement. The changes leverage modern PHP features to improve code quality and maintainability.

• Updated minimum PHP version requirement from 7.2 to 8.1
• Refactored code to use PHP 8.1+ features like constructor property promotion, union types, and match expressions
• Enhanced type declarations throughout the codebase

Reviewed Changes

Copilot reviewed 33 out of 34 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
composer.json	Updated PHP version constraint to require 8.1+ and modernized dev dependencies
rector.php	Added new Rector configuration file to enforce PHP 8.1 standards
src/OpenTok/*.php	Modernized core classes with constructor property promotion, match expressions, and improved type safety
src/OpenTok/Util/*.php	Updated utility classes with modern PHP features and stricter type checking
tests/OpenTokTest/*.php	Enhanced test files with return type declarations and modern syntax
sample/*.php	Updated sample applications to use modern array syntax and arrow functions

Comments suppressed due to low confidence (2)

tests/OpenTokTest/OpenTokTest.php:1

• Inconsistent comment placement and missing elseif structure. The TODO comment should be moved outside the control flow and the conditional should use 'elseif' for better readability.

<?php

tests/OpenTokTest/OpenTokTest.php:1

• [nitpick] Complex nested array operations with arrow functions make this line difficult to read. Consider breaking this into multiple lines for better maintainability.

<?php

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