rework mongodb index creation in spring data 3.x

[basalt79]

2020-03-14 08:37:27.725  WARN 16540 --- [           main] .m.c.i.MongoPersistentEntityIndexCreator : Automatic index creation will be disabled by default as of Spring Data MongoDB 3.x.
	Please use 'MongoMappingContext#setAutoIndexCreation(boolean)' or override 'MongoConfigurationSupport#autoIndexCreation()' to be explicit.
	However, we recommend setting up indices manually in an application ready block. You may use index derivation there as well.

	> -----------------------------------------------------------------------------------------
	> @EventListener(ApplicationReadyEvent.class)
	> public void initIndicesAfterStartup() {
	>
	>     IndexOperations indexOps = mongoTemplate.indexOps(DomainType.class);
	>
	>     IndexResolver resolver = new MongoPersistentEntityIndexResolver(mongoMappingContext);
	>     resolver.resolveIndexFor(DomainType.class).forEach(indexOps::ensureIndex);
	> }
	> -----------------------------------------------------------------------------------------