Documentation
* docs: add apple pay transformer usage to readme ([cad0caeae8a87a127cc5d8b4361ffb3d40701177](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/cad0caeae8a87a127cc5d8b4361ffb3d40701177))
* docs: add contributing guidelines and update readme ([ebdae42561c980a022650fef5154b84fe853379c](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/ebdae42561c980a022650fef5154b84fe853379c))
* docs: update readme ([035d54c32c5a969474ebaec68de3749fcb6a7684](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/035d54c32c5a969474ebaec68de3749fcb6a7684))
Features
* feat: add an example for every endpoint of the commerce case api client ([d8870eb501d77427998308b62f57b7ee398257d9](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/d8870eb501d77427998308b62f57b7ee398257d9))
* feat: add apple pay ([5f9cebb3835860a95e0a6dd3ed365e99d2096ebc](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/5f9cebb3835860a95e0a6dd3ed365e99d2096ebc))
* feat: add error classes ([322b27b3d2b5c396220e3140c99a613e99e05a24](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/322b27b3d2b5c396220e3140c99a613e99e05a24))
* feat: add example ([4a61f7caafcdb459573154a81b2185aa44392fe4](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/4a61f7caafcdb459573154a81b2185aa44392fe4))
* feat: add more endpoints ([a26bbb71de8e083e55f83ad0ca12149ce0a09978](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/a26bbb71de8e083e55f83ad0ca12149ce0a09978))
* feat: add order management checkout actions api client ([243a949101ed57bb5a5e4139e324b98764373639](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/243a949101ed57bb5a5e4139e324b98764373639))
* feat: add payment execution api client ([1ed7a9452805245efe0ff332f6afdd4bec3e5c36](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/1ed7a9452805245efe0ff332f6afdd4bec3e5c36))
* feat: add payment information api client ([7db61d3b7af57de6d907380b2ba7b306eddddb27](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/7db61d3b7af57de6d907380b2ba7b306eddddb27))
* feat: add payment information example ([e649895340dcdbae09e02ee10a4bcc3cefc26ec1](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/e649895340dcdbae09e02ee10a4bcc3cefc26ec1))
* feat: add RequestHeaderGenerator ([c93e9f20e0d813feff30adb50f5c815f562efc1d](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/c93e9f20e0d813feff30adb50f5c815f562efc1d))
* feat: init commerce case api client for managing commerce cases ([df92f9d5c8a68da796d9ecf7d4943d5a75930917](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/df92f9d5c8a68da796d9ecf7d4943d5a75930917))
* feat(models): add models and api client ([3f622d9086e19f8ba58f6e3e364134526b04af51](https://github.com/PAYONE-GmbH/PCP-ServerSDK-java/commit/3f622d9086e19f8ba58f6e3e364134526b04af51))