fix: Eagerly load DBSchedulerStarter (491) (#492)

## Brief, plain english overview of your changes here
Excludes DbSchedulerStarter from being lazily initialized.

## Fixes
The DbSchedulerStarter isn't created in a application where lazy
initialization is enabled via `spring.main.lazy-initialization=true`.

Fixes: #491

## Reminders
- [X] Added/ran automated tests
- [ ] Update README and/or examples
- [x] Ran `mvn spotless:apply`

db-scheduler-boot-starter/src/main/java/com/github/kagkarlsson/scheduler/boot/autoconfigure/DbSchedulerAutoConfiguration.java

@@ -39,6 +39,7 @@
 import javax.sql.DataSource;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.springframework.boot.LazyInitializationExcludeFilter;
 import org.springframework.boot.autoconfigure.AutoConfigurationPackage;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
@@ -192,6 +193,11 @@ public DbSchedulerStarter dbSchedulerStarter(Scheduler scheduler) {
     return new ImmediateStart(scheduler);
   }
 
+  @Bean
+  public LazyInitializationExcludeFilter eagerDbSchedulerStarter() {
+    return LazyInitializationExcludeFilter.forBeanTypes(DbSchedulerStarter.class);
+  }
+
   private static DataSource configureDataSource(DataSource existingDataSource) {
     if (existingDataSource instanceof TransactionAwareDataSourceProxy) {
       log.debug("Using an already transaction aware DataSource");

db-scheduler-boot-starter/src/test/java/com/github/kagkarlsson/scheduler/boot/autoconfigure/DbSchedulerAutoConfigurationTest.java

@@ -29,6 +29,7 @@
 import org.junit.jupiter.api.Test;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.springframework.boot.LazyInitializationExcludeFilter;
 import org.springframework.boot.actuate.autoconfigure.health.HealthContributorAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.metrics.CompositeMeterRegistryAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.metrics.MetricsAutoConfiguration;
@@ -241,6 +242,17 @@ public void it_should_use_custom_stats_registry_if_present_in_context() {
             });
   }
 
+  @Test
+  void it_should_exclude_db_scheduler_starter_from_lazy_init() {
+    ctxRunner.run(
+        (context) -> {
+          LazyInitializationExcludeFilter filter =
+              context.getBean(LazyInitializationExcludeFilter.class);
+
+          assertThat(filter.isExcluded(null, null, DbSchedulerStarter.class)).isTrue();
+        });
+  }
+
   @Configuration
   static class SingleTaskConfiguration {
     @Bean