What is TestReporter in JUnit 6 and how do you use it?

import org.junit.jupiter.api.TestReporter;

class TestReporterDemo {

    @Test
    void reportingDemo(TestReporter reporter) {
        // Publish a single key-value entry
        reporter.publishEntry("user-id", "U-12345");
        reporter.publishEntry("status", "active");

        // Publish a map of entries in one call
        Map<String, String> values = Map.of(
            "order-id",   "O-99",
            "total",      "149.99",
            "currency",   "GBP"
        );
        reporter.publishEntry(values);

        // Assertions still run after publishing entries
        assertTrue(true);
    }

    @Test
    void reportWithMessage(TestReporter reporter) {
        // Single-argument form: just a message string
        reporter.publishEntry("Processing payment for order O-42");
    }
}

// TestReporter vs System.out:
//
// System.out.println:
//   - Goes to process stdout
//   - Not associated with any specific test in the report
//   - Lost in CI log noise
//
// TestReporter.publishEntry:
//   - Attached to the specific test result
//   - Appears in IDE test runner output alongside the test
//   - Included in XML/HTML test reports
//   - Visible when you click on a specific test result in the IDE