Replace Moshi with Micronaut Serde (Serde 3 / JDK 25 / Gradle 9)

[MariusVolkhart]

What & why

Replaces the Moshi-based JSON converter patch with Micronaut Serde, eliminating jackson-databind and moshi from the runtime classpath. Drivers: kill jackson-databind, match the production stack (Micronaut 5 / Serde 3), and Serde-generated codecs beat Moshi on deserialize.

Because Micronaut Serde 3.x requires JVM 17+, this also bumps the published fork to JDK 25 / Gradle 9.

Patches

• 0001 Replace Jackson with Micronaut Serde — json/plain default is now MicronautSerdePayloadConverter over the application's injected io.micronaut.serde.ObjectMapper. SDK-internal protocol JSON (operation tokens, local-activity markers, failure encoding) uses a library-private mapper. Also carries the JDK-25/Gradle-9 build infra (wrapper 9.6.1, --release 25, Mockito 5.23.0, logback 1.5.18, Error Prone disabled on the JVM-25 modules).
• 0002 / 0003 grpc-netty / groupId — replayed unchanged.
• 0004 Add Wire protobuf support — Wire Message types serialize as native protobuf binary (protobuf/wire); the Moshi WireJsonAdapterFactory (nested-Wire-in-JSON) path is removed.

Architecture notes

• User payloads use your injected ObjectMapper; SDK-internal serialization uses a separate library-private mapper, so the SDK-specific formats (Duration-as-millis, OperationTokenType-as-int) never touch your data.
• Those SDK-specific serdes are typed Serde<Object> and bound via field using=, so they are not globally indexed and do not leak into a consuming app's DI ObjectMapper (verified by SerdeIsolationTest against a real ApplicationContext).

Consumer behavior changes (vs the old Jackson/Moshi converter)

Micronaut Serde is reflection-free / compile-time, so:

• Workflow arg/result types must be @Serdeable (your Micronaut 5 models already are).
• Public-field POJOs serialize to {} — use records, getters, or @Introspected(accessKind = {FIELD, METHOD}).
• java.time.Duration serializes as integer nanoseconds (Serde default), not an ISO-8601 string.
• An empty byte[] field inside a large bean may deserialize as null.
• Wire Message types are protobuf-binary, not JSON.

Verification

• All 4 patches apply cleanly from a fresh upstream clone.
• Full compile green at JDK 25 / Gradle 9.
• Dependency gate clean: no jackson-databind, no moshi (okio remains only as a wire-runtime transitive).
• Best clean full run: 1510 tests, 1 failure.

One deterministic test failure remains — SearchAttributesTest.testInvalidSearchAttributeType. It is not a Serde-converter regression: the search-attribute encode path, SearchAttributePayloadConverter, and the test-server validation are byte-identical to upstream (the only SA-path file this PR touches is temporal-test-server/build.gradle, a build-only change), and the test starts a no-arg workflow so the data converter is barely involved. It is the in-process test server's invalid-type-rejection behavior under JDK 25; production search-attribute validation is unaffected (a real Temporal server validates server-side, and the SDK sends the same encoding as upstream). It likely reproduces on upstream-at-JDK-25 and should be triaged as a JDK-25 test-infra item. Please confirm the suite in CI (now JDK 25) on adequate resources — the parallel test suite flakes badly under machine load.

Note

.github/workflows/manual-build.yml also includes a pre-existing uncommitted version_override workflow input (unrelated working-tree edit) that got bundled with the JDK-25 change.

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