OZG-6638 conditional bean initialization

ozg-cloud-spring-boot-starter/src/main/java/de/ozgcloud/client/autoconfigure/OzgCloudClientAutoConfiguration.java

@@ -135,8 +135,8 @@ public class OzgCloudClientAutoConfiguration {
 
 	@Bean("ozgCloudVorgangService")
 	@ConditionalOnProperty("ozgcloud.vorgang-manager.address")
-	OzgCloudVorgangService grpcOzgCloudVorgangService(VorgangServiceBlockingStub vorgangServiceStub,
-			OzgCloudVorgangMapper mapper,
+	@ConditionalOnMissingBean(OzgCloudVorgangService.class)
+	OzgCloudVorgangService grpcOzgCloudVorgangService(VorgangServiceBlockingStub vorgangServiceStub, OzgCloudVorgangMapper mapper,
 			OzgCloudVorgangStubMapper stubMapper, OzgCloudCallContextProvider contextProvider) {
 
 		return new GrpcOzgCloudVorgangService(vorgangServiceStub, mapper, stubMapper, contextProvider);