feat: improved async performance with thread-safe type (#381)

[petruki]

This pull request refactors how the SwitcherBuilder and its implementation SwitcherRequest manage the history of executions, improves thread safety, and simplifies several null checks throughout the codebase. The most significant changes include moving the historyExecution map from the abstract builder to the concrete request class and switching to a thread-safe implementation, as well as updating null checks to use Objects.nonNull and Objects.isNull for clarity and consistency.

Refactoring and Thread Safety

• Moved the historyExecution map from SwitcherBuilder to SwitcherRequest, and changed its implementation to use ConcurrentHashMap for thread safety. (src/main/java/com/switcherapi/client/model/SwitcherBuilder.java [1] [2]; src/main/java/com/switcherapi/client/model/SwitcherRequest.java [3] [4]
• Updated the flush() method in SwitcherBuilder to be abstract, and implemented it in SwitcherRequest to clear both entry and historyExecution. (src/main/java/com/switcherapi/client/model/SwitcherBuilder.java [1]; src/main/java/com/switcherapi/client/model/SwitcherRequest.java [2]

These changes collectively improve the maintainability, thread safety, and readability of the codebase.

[Before] Operations /s in 5s

Benchmark	Type	Mode	Score	Units
ClientJavaBenchmark.testSwitcherRemoteThrottle	Async	thrpt	40,171,215.842	ops/s
ClientJavaBenchmark.testSwitcherLocal	Local	thrpt	19,689,072.262	ops/s

[After] Operations /s in 5s

Benchmark	Type	Mode	Score	Units
ClientJavaBenchmark.testSwitcherRemoteThrottle	Async	thrpt	109,325,445.942	ops/s
ClientJavaBenchmark.testSwitcherLocal	Local	thrpt	41,501,007.578	ops/s

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
94.1% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud