Downgrade drools to 8.27.0.Beta to ensure Java 8 compatibility (#253)

* Use drools 8.27.0.Beta instead of 8.44.0.Finals as 8.28.0 or higher breaks Java 8 compatibility.

* Workaround to avoid https://issues.redhat.com/browse/DROOLS-7210

core/pom.xml

@@ -73,17 +73,17 @@
     <dependency>
       <groupId>org.kie</groupId>
       <artifactId>kie-ci</artifactId>
-      <version>8.44.0.Final</version>
+      <version>8.27.0.Beta</version>
     </dependency>
     <dependency>
       <groupId>org.drools</groupId>
       <artifactId>drools-decisiontables</artifactId>
-      <version>8.44.0.Final</version>
+      <version>8.27.0.Beta</version>
     </dependency>
     <dependency>
       <groupId>org.drools</groupId>
       <artifactId>drools-xml-support</artifactId>
-      <version>8.44.0.Final</version>
+      <version>8.27.0.Beta</version>
     </dependency>
     <dependency>
       <groupId>org.apache.poi</groupId>

core/src/main/java/com/devonfw/tools/solicitor/ruleengine/drools/DroolsRuleEngine.java

@@ -19,6 +19,7 @@
 import org.kie.api.io.Resource;
 import org.kie.api.runtime.KieContainer;
 import org.kie.api.runtime.KieSession;
+import org.kie.internal.builder.conf.ParallelRulesBuildThresholdOption;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -49,6 +50,12 @@
 @Order(InventoryProcessor.RULE_ENGINE)
 public class DroolsRuleEngine implements RuleEngine {
 
+  static {
+    // avoid parallel compiling of rules to avoid bug existing in Drools 8.17.0.Beta ... 8.31.0.Beta
+    // see https://issues.redhat.com/browse/DROOLS-7210
+    System.setProperty(ParallelRulesBuildThresholdOption.PROPERTY_NAME, "-1");
+  }
+
   private static final Logger LOG = LoggerFactory.getLogger(DroolsRuleEngine.class);
 
   @Value("${drools-rule-engine.debuglog}")

documentation/master-solicitor.asciidoc

@@ -1701,7 +1701,7 @@ Spring beans implementing this interface will be called at certain points in the
 == Release Notes
 Changes in 1.22.0::
 * https://github.com/devonfw/solicitor/pull/243: Make sure the MavenReader is protected against XXE threats.
-* https://github.com/devonfw/solicitor/pull/244: Updated Drools rule engine to 8.44.0.Final.
+* https://github.com/devonfw/solicitor/pull/244: Updated Drools rule engine to 8.27.0.Beta.
 * https://github.com/devonfw/solicitor/issues/247: Running Solicitor on Java 8 is deprecated (Stage 1) and will be no longer possible soon. Move to Java 11 ASAP!
 
 Changes in 1.21.0::