App-store-server-library

- Incorporate changes for App Store Server API v1.15 and App Store Server Notifications v2.15 [https://github.com/apple/app-store-server-library-java/pull/152]

- Update BaseAppStoreServerAPIClient to move URL selection to a method [https://github.com/apple/app-store-server-library-java/pull/136]

- Incorporate caching of validated certificate chains to prevent repetitive OCSP fetches [https://github.com/apple/app-store-server-library-java/pull/127]

- Incorporate changes for App Store Server API v1.13 and App Store Server Notifications v2.13 [https://github.com/apple/app-store-server-library-java/pull/116]
- Handle parsing empty or unexpected bodies on API exceptions without throwing a caused-by exception [https://github.com/apple/app-store-server-library-java/pull/119]

- Allow providing a custom bearer token provider and HTTP client implementation [https://github.com/apple/app-store-server-library-java/pull/109]
- This change refactors the internal implementation of the AppStoreServerAPIClient class. Users extending this class may see interface changes
- Rename applicationUsername to appAccountToken [https://github.com/apple/app-store-server-library-java/pull/104]

- Incorporate changes for App Store Server API v1.13 and App Store Server Notifications v2.13 [https://github.com/apple/app-store-server-library-swift/pull/61]
- Resolve issue where a Date passed as an input that contained a microsecond portiion would cause an API exception [https://github.com/apple/app-store-server-library-swift/pull/62]