made exector service configurable again

Author: jonathanlukas

spring-boot-starter-camunda/src/main/java/io/camunda/zeebe/spring/client/configuration/ZeebeClientAllAutoConfiguration.java

@@ -39,7 +39,8 @@ public ZeebeClientAllAutoConfiguration(ZeebeClientConfigurationProperties config
   @Bean
   @ConditionalOnMissingBean
   public ZeebeClientExecutorService zeebeClientExecutorService() {
-    return ZeebeClientExecutorService.createDefault();
+    return ZeebeClientExecutorService.createDefault(
+        configurationProperties.getNumJobWorkerExecutionThreads());
   }
 
   @Bean

spring-client-zeebe/src/main/java/io/camunda/zeebe/spring/client/jobhandling/ZeebeClientExecutorService.java

@@ -23,7 +23,11 @@ public ScheduledExecutorService get() {
   }
 
   public static ZeebeClientExecutorService createDefault() {
-    ScheduledExecutorService threadPool = Executors.newSingleThreadScheduledExecutor();
+    return createDefault(1);
+  }
+
+  public static ZeebeClientExecutorService createDefault(int threads) {
+    ScheduledExecutorService threadPool = Executors.newScheduledThreadPool(threads);
     return new ZeebeClientExecutorService(threadPool);
   }