Optimization and changes for relevant issues.

[RZEROSTERN]

This pull request introduces a major release (v1.2) with significant enhancements to reliability, configurability, and developer tooling for the notification core library. Key improvements include support for PSR-16 token caching, robust automatic retry logic for transient errors, expanded error handling, and a comprehensive CI/CD pipeline with enforced code coverage. Several breaking changes and bug fixes are also included to improve consistency and compatibility.

Major feature additions:

• Added optional PSR-16 cache support to GoogleServiceAccountTokenProvider via a new constructor argument and config options (cache_key), enabling OAuth tokens to be shared across processes/requests. (src/Auth/GoogleServiceAccountTokenProvider.php, composer.json, README.md, CHANGELOG.md) [1] [2] [3] [4] [5] [6] [7]
• Implemented automatic retry with exponential backoff and jitter for transient failures (HTTP 5xx, 429, PSR-18 transport errors) in both the token provider and FcmHttpV1Client, configurable via max_retries and retry_base_delay_ms. (src/Auth/GoogleServiceAccountTokenProvider.php, CHANGELOG.md) [1] [2]
• Added a comprehensive GitHub Actions CI/CD pipeline: matrix tests on PHP 7.4–8.4, ≥80% coverage enforcement, auto-tagging on master, and coverage badge publishing. (.github/workflows/ci.yml, README.md, CHANGELOG.md) [1] [2] [3]
• Introduced PHPUnit configuration and an initial test suite covering all major components. (phpunit.xml.dist, .phpunit.result.cache, composer.json, README.md, CHANGELOG.md) [1] [2] [3] [4] [5]

Breaking changes and enhancements:

• PushTarget now throws on ambiguous or multiple targets; AndroidOptions::withPriority() throws on unknown values; improved error handling and return types across several classes; widened psr/log version constraint for broader compatibility. (src/Auth/GoogleServiceAccountTokenProvider.php, composer.json, CHANGELOG.md) [1] [2] [3]

Documentation and metadata:

• Updated README.md badges, features, and roadmap to reflect new CI, coverage, and cache/retry capabilities. (README.md, CHANGELOG.md) [1] [2] [3]

Testing and developer experience:

• Added Composer scripts and autoloading for tests; suggested psr/simple-cache for shared token caching. (composer.json, phpunit.xml.dist, CHANGELOG.md) [1] [2] [3]

These changes collectively deliver a more robust, configurable, and testable notification core library, preparing it for broader adoption and easier integration into modern PHP projects.