[FEATURE] Support for Jackson 3.0 (Jakarta EE 11 / Spring Boot 4 compatibility)

[efmaster]

Describe the problem you'd like to have solved

With the release of Spring Boot 4.0, the Java ecosystem is transitioning to Jackson 3.0 as the primary JSON library. Spring Boot 4 has moved its auto-configuration baseline to the new Jackson 3 packages (tools.jackson.*).

Currently, the OpenFGA Java SDK is strictly tied to Jackson 2.x. When using the SDK in a Spring Boot 4 environment, we encounter significant friction:

• Dependency Bloat: We are forced to keep both Jackson 2 and Jackson 3 on the classpath.

• Configuration Conflicts: Spring Boot 4’s auto-configuration defaults to Jackson 3, making it difficult to seamlessly integrate the OpenFGA SDK’s Jackson 2-based models into the global object mapper without complex workarounds.

• Future-proofing: Official documentation suggests that Jackson 2 support in the Spring ecosystem will be phased out entirely (expected by Spring Boot 4.3).

Describe the ideal solution

The ideal solution would be a version of the OpenFGA Java SDK that natively supports Jackson 3.0 (using the tools.jackson namespace).

Since this involves a change in package names and a move to Jakarta EE 11, this might be released as a new major version of the SDK to avoid breaking changes for users still on Jackson 2/Spring Boot 3. Alternatively, a modular approach or a shaded version could be considered to support both ecosystems during the transition period.

Alternatives and current workarounds

Currently, the only workaround is to run a dual-stack configuration where Jackson 2 and Jackson 3 coexist. This is highly discouraged for production environments as it leads to:

1. Inconsistent serialization/deserialization behavior.

2. Manual configuration of the OpenFgaClient to ensure it uses the "old" Jackson 2 mapper while the rest of the application uses Jackson 3.

3. Increased binary size and potential classpath "jar hell."

Additional context

Spring Boot 4 also introduces a shift toward JSpecify for null-safety. Aligning the SDK with Jackson 3 and modern Jakarta/Spring standards will ensure that OpenFGA remains a first-class citizen in the modern Java cloud-native stack. This request is a prerequisite for updating the openfga-spring-boot-starter to be compatible with Spring Boot 4.

[rhamzeh]

Thanks for the suggestion @efmaster!

@jimmyjames I would defer to you here - would upgrading to Jackson 3 be a breaking change for our community? If yes, do we know how many generally are using 2 over 3 or vice-versa?

I'm guessing at the very least this would deserve a callout in the CHANGELOG and bumping to v0.10.0?