Issue #389: update to checkstyle 9.1

Author: muhlba91

README.md

@@ -15,12 +15,13 @@ Official announcement of project transfer - https://groups.google.com/d/topic/so
 
 This plugin provides coding rules from [Checkstyle](http://checkstyle.sourceforge.net/).
 
-Compatibility matrix from Sonar team: https://docs.sonarqube.org/display/PLUG/Plugin+Version+Matrix
+Compatibility matrix from Sonar team: https://docs.sonarqube.org/latest/instance-administration/plugin-version-matrix/
 
 Compatibility matrix from checkstyle team:
 
 Checkstyle Plugin|Sonar min|Sonar max|Checkstyle|Jdk
 -----------------|---------|---------|----------|---
+9.1|8.9  |8.9+|9.1|1.8
 9.0.1|8.9  |8.9+|9.0.1|1.8
 8.45.1|7.9  |7.9+|8.45.1|1.8
 8.42|7.9  |7.9+|8.42|1.8

pom.xml

@@ -93,7 +93,7 @@
   </ciManagement>
 
   <properties>
-    <checkstyle.version>9.0.1</checkstyle.version>
+    <checkstyle.version>9.1</checkstyle.version>
     <sonar.version>8.9.3.48735</sonar.version>
     <sonar-java.version>7.2.0.26923</sonar-java.version>
     <maven.checkstyle.plugin.version>3.1.2</maven.checkstyle.plugin.version>
@@ -318,7 +318,7 @@
     <dependency>
         <groupId>org.reflections</groupId>
         <artifactId>reflections</artifactId>
-        <version>0.9.12</version>
+        <version>0.10.2</version>
     </dependency>
   </dependencies>
 
@@ -843,9 +843,9 @@
         </executions>
       </plugin>
       <plugin>
-        <groupId>org.codehaus.mojo</groupId>
+        <groupId>org.sonarsource.scanner.maven</groupId>
         <artifactId>sonar-maven-plugin</artifactId>
-        <version>3.9.0.2155</version>
+        <version>3.9.1.2184</version>
       </plugin>
     </plugins>
   </build>

test-resources/docker-compose.yml

@@ -4,7 +4,9 @@ version: "3"
 services:
   sonarqube:
     image: sonarqube:8.9.3-community
-    # next line is for arm64 devices when testing since SQ does not officially release multi-arch images
+    # alternatively, to test with 9.1, use the next line
+    #image: sonarqube:9.1-community
+    # next line is for arm64 devices (e.g. Mac M1) when testing since SQ does not officially release multi-arch images
     #image: stevefan1999/sonarqube:9.0.1-community
     restart: unless-stopped
     depends_on: