Fix #475: Incompatible date serialization default with Jackson 3

[romanstrobl]

No description provided.

[Copilot]

Pull request overview

This pull request addresses issue #475 by restoring the historical behavior of DefaultRestClient JSON serialization for date/time values after Jackson 3 changed the default for WRITE_DATES_AS_TIMESTAMPS.

Changes:

• Force-enable timestamp-based date serialization in the DefaultRestClient Jackson JsonMapper builder (to avoid ISO-8601 strings by default).
• Add a regression test that verifies java.util.Date is serialized as numeric epoch milliseconds in POST bodies.
• Add a test-only controller endpoint that echoes the raw JSON request body to make the serialization assertion reliable.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
rest-client-base/src/main/java/com/wultra/core/rest/client/base/DefaultRestClient.java	Enables DateTimeFeature.WRITE_DATES_AS_TIMESTAMPS when creating the client JsonMapper to preserve pre-Jackson-3 wire format.
rest-client-base/src/test/java/com/wultra/core/rest/client/base/DefaultRestClientTest.java	Adds a regression test validating numeric timestamp serialization for Date by inspecting the echoed raw request JSON.
rest-client-base/src/test/java/com/wultra/core/rest/client/base/controller/PublicTestRestController.java	Adds an endpoint to echo the raw JSON request body used by the new regression test.

[banterCZ]

May we please backport this test to 2.1.x just to be sure about this complicated issue?

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

Suppressed comments (1)

rest-client-base/src/test/java/com/wultra/core/rest/client/base/DefaultRestClientTest.java:310

• The assertions rely on substring matching in the echoed JSON (e.g., exact spacing and a hard-coded ISO-8601 prefix). This can make the regression test brittle if the JSON generator changes formatting (whitespace, ordering) while still serializing the date correctly. Consider parsing the echoed body as JSON and asserting that timestamp is a numeric node with the expected epoch value.

        assertTrue(rawBody.contains("\"timestamp\":1785926829449"),
                "Date must be serialized as numeric epoch milliseconds, was: " + rawBody);
        assertFalse(rawBody.contains("2026-08-"),
                "Date must not be serialized as an ISO-8601 string, was: " + rawBody);