MINOR: Log at info level when pending member joins a group (apache#17495)

When a dynamic member joins a group, it sends two JOIN_GROUP requests.
The first request doesn't have a member id and returns
MEMBER_ID_REQUIRED with a broker-generated member id. The second request
includes the broker-generated member id and joins the group for real.

We emit a log message at info level for the first join request, but not
the second. Log the second join request at info level too.

Reviewers: David Jacot <[email protected]>

Author: squah-confluent

core/src/main/scala/kafka/coordinator/group/GroupCoordinator.scala

@@ -427,7 +427,7 @@ private[group] class GroupCoordinator(
             s"for pending member with memberId=$memberId")
         }
 
-        debug(s"Pending dynamic member with id $memberId joins group ${group.groupId} in " +
+        info(s"Pending dynamic member with id $memberId joins group ${group.groupId} in " +
           s"${group.currentState} state. Adding to the group now.")
         addMemberAndRebalance(rebalanceTimeoutMs, sessionTimeoutMs, memberId, None,
           clientId, clientHost, protocolType, protocols, group, responseCallback, reason)

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/GroupMetadataManager.java

@@ -4321,7 +4321,7 @@ private CoordinatorResult<Void, CoordinatorRecord> classicGroupJoinExistingMembe
                     groupInstanceId + " for pending member with memberId=" + memberId);
             }
 
-            log.debug("Pending dynamic member with id {} joins group {} in {} state. Adding to the group now.",
+            log.info("Pending dynamic member with id {} joins group {} in {} state. Adding to the group now.",
                 memberId, group.groupId(), group.currentState());
 
             return addMemberThenRebalanceOrCompleteJoin(