Fix projects stats export worker

java.lang.RuntimeException: java.io.NotSerializableException: com.nuxeo.connect.stats.util.ExternalDBConnector
	at org.nuxeo.ecm.core.redis.contribs.RedisBlockingQueue.putElement(RedisBlockingQueue.java:135) ~[nuxeo-core-redis-2021.19.10.jar:?]
	at org.nuxeo.ecm.core.work.NuxeoBlockingQueue.put(NuxeoBlockingQueue.java:108) ~[nuxeo-core-event-2021.19.10.jar:?]
	at org.nuxeo.ecm.core.work.NuxeoBlockingQueue.offer(NuxeoBlockingQueue.java:91) ~[nuxeo-core-event-2021.19.10.jar:?]
	at org.nuxeo.ecm.core.redis.contribs.RedisWorkQueuing.workSchedule(RedisWorkQueuing.java:186) ~[nuxeo-core-redis-2021.19.10.jar:?]
	at org.nuxeo.ecm.core.work.WorkManagerImpl.schedule(WorkManagerImpl.java:836) ~[nuxeo-core-event-2021.19.10.jar:?]
	at org.nuxeo.ecm.core.work.WorkManagerImpl.schedule(WorkManagerImpl.java:787) ~[nuxeo-core-event-2021.19.10.jar:?]
	at com.nuxeo.connect.stats.ProjectStatsExtractionSchedulerWork.lambda$work$0(ProjectStatsExtractionSchedulerWork.java:42) ~[nuxeo-connect-plugin-2022.4.2-0-g9f7b3884.jar:?]
	at com.nuxeo.connect.stats.ProjectStatsExtractionSchedulerWork.lambda$queryDocuments$2(ProjectStatsExtractionSchedulerWork.java:51) ~[nuxeo-connect-plugin-2022.4.2-0-g9f7b3884.jar:?]
	at java.lang.Iterable.forEach(Iterable.java:75) ~[?:?]
	at com.nuxeo.connect.stats.ProjectStatsExtractionSchedulerWork.queryDocuments(ProjectStatsExtractionSchedulerWork.java:51) ~[nuxeo-connect-plugin-2022.4.2-0-g9f7b3884.jar:?]
	at com.nuxeo.connect.stats.ProjectStatsExtractionSchedulerWork.lambda$work$1(ProjectStatsExtractionSchedulerWork.java:40) ~[nuxeo-connect-plugin-2022.4.2-0-g9f7b3884.jar:?]
	at org.nuxeo.ecm.core.api.CoreInstance$3.run(CoreInstance.java:268) ~[nuxeo-core-api-2021.19.10.jar:?]
	at org.nuxeo.ecm.core.api.UnrestrictedSessionRunner.runUnrestricted(UnrestrictedSessionRunner.java:123) ~[nuxeo-core-api-2021.19.10.jar:?]
	at org.nuxeo.ecm.core.api.CoreInstance.doPrivileged(CoreInstance.java:270) ~[nuxeo-core-api-2021.19.10.jar:?]
	at com.nuxeo.connect.stats.ProjectStatsExtractionSchedulerWork.work(ProjectStatsExtractionSchedulerWork.java:39) ~[nuxeo-connect-plugin-2022.4.2-0-g9f7b3884.jar:?]
	at org.nuxeo.ecm.core.work.AbstractWork.runWorkWithTransaction(AbstractWork.java:536) [nuxeo-core-event-2021.19.10.jar:?]
	at org.nuxeo.ecm.core.work.AbstractWork.run(AbstractWork.java:387) [nuxeo-core-event-2021.19.10.jar:?]
	at org.nuxeo.ecm.core.work.WorkHolder.run(WorkHolder.java:57) [nuxeo-core-event-2021.19.10.jar:?]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
	at java.lang.Thread.run(Thread.java:829) [?:?]
Caused by: java.io.NotSerializableException: com.nuxeo.connect.stats.util.ExternalDBConnector
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1185) ~[?:?]
	at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1553) ~[?:?]
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1510) ~[?:?]
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1433) ~[?:?]
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1179) ~[?:?]
	at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:349) ~[?:?]
	at org.nuxeo.ecm.core.redis.contribs.RedisWorkQueuing.serializeWork(RedisWorkQueuing.java:425) ~[nuxeo-core-redis-2021.19.10.jar:?]
	at org.nuxeo.ecm.core.redis.contribs.RedisWorkQueuing.args(RedisWorkQueuing.java:583) ~[nuxeo-core-redis-2021.19.10.jar:?]
	at org.nuxeo.ecm.core.redis.contribs.RedisWorkQueuing.workSetScheduled(RedisWorkQueuing.java:534) ~[nuxeo-core-redis-2021.19.10.jar:?]
	at org.nuxeo.ecm.core.redis.contribs.RedisBlockingQueue.putElement(RedisBlockingQueue.java:131) ~[nuxeo-core-redis-2021.19.10.jar:?]
	... 20 more