Feature/general improvements

[sn]

This pull request introduces several improvements to the CI/CD workflow, enhances code coverage handling for different environments, updates configuration files for modern PHPUnit compatibility, and makes minor bug fixes and documentation improvements. The most significant changes are grouped below.

CI/CD Workflow and Code Coverage Improvements:

• The .github/workflows/ci.yml workflow has been updated to improve coverage handling: PCOV is explicitly installed, tests are run with coverage output, and coverage upload now uses a dedicated script (ci/run_coverage.sh) for better compatibility and robustness. [1] [2] [3]
• Added new scripts ci/run_coverage.sh (Bash) and ci/coverage.php (PHP) to conditionally run tests and generate coverage reports based on the presence of coverage drivers (xdebug/pcov), including fallback to placeholder coverage files if no driver is available. [1] [2]
• Introduced ci/generate_phpunit_config.php to generate PHPUnit configuration files dynamically based on detected PHPUnit version, improving compatibility across environments.

PHPUnit Configuration Modernization:

• Updated phpunit.xml.dist to use the modern schema, with improved coverage configuration and removal of legacy <filter> and <logging> sections, making it compatible with PHPUnit 9+.

Code Quality and Bug Fixes:

• Fixed a bug in polyfill_filter_var_string in gump.class.php to properly escape single and double quotes and corrected a regex typo.
• Standardized method signatures in gump.class.php for several validators to ensure default values and type consistency. [1] [2] [3] [4] [5] [6] [7] [8] [9]

Testing Enhancements:

• Added a comprehensive new test suite for the upper_case filter in tests/Filters/UpperCaseFilterTest.php, covering a wide range of input scenarios including Unicode, special characters, and edge cases.

Documentation and Metadata Updates:

• Updated author homepage in composer.json and copyright notice in LICENSE. [1] [2]
• Added missing ArrayAccess import in src/ArrayHelpers.php.