test: Add parameterized unit tests for context payload serialization

[Olti1947]

Description

We need comprehensive parameterized unit tests using JUnit 5 (@ParameterizedTest) to verify that various Java data types within the context payload (Java 17 Records, nested Maps, List collections, null values, Primitives) serialize cleanly to JSON without missing fields or raising Jackson mapping exceptions.

Acceptance Criteria

• Add @ParameterizedTest cases in JevClientTest.java.
• Verify serialization for Java 17 record classes as context payloads.
• Verify handling of empty/null values within context maps.