KAFKA-18320; Ensure that assignors are at the right place (#18750)

The full class name of the assignors if part of our public api. Hence, we should ensure that they are not changed by mistake. This patch adds a unit test verifying them.

Reviewers: Sean Quah <squah@confluent.io>, Jeff Kim <jeff.kim@confluent.io>

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/GroupCoordinatorConfigTest.java

@@ -44,6 +44,19 @@ public class GroupCoordinatorConfigTest {
             GroupCoordinatorConfig.CONSUMER_GROUP_CONFIG_DEF,
             GroupCoordinatorConfig.SHARE_GROUP_CONFIG_DEF);
 
+    @Test
+    public void testConsumerGroupAssignorsDefault() {
+        // The full class name of the assignors is part of our public api. Hence,
+        // we should ensure that they are not changed by mistake.
+        assertEquals(
+            List.of(
+                "org.apache.kafka.coordinator.group.assignor.UniformAssignor",
+                "org.apache.kafka.coordinator.group.assignor.RangeAssignor"
+            ),
+            GroupCoordinatorConfig.CONSUMER_GROUP_ASSIGNORS_DEFAULT
+        );
+    }
+
     @Test
     public void testConfigs() {
         Map<String, Object> configs = new HashMap<>();