WIPP for JDK21 migration

pom.xml

@@ -5,17 +5,17 @@
     <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-parent</artifactId>
-        <version>2.7.6</version>
+        <version>2.7.18</version>
         <relativePath/> <!-- lookup parent from repository -->
     </parent>
     <groupId>org.surfnet</groupId>
     <artifactId>student-mobility-inteken-ontvanger-email</artifactId>
-    <version>0.2.12</version>
+    <version>0.3.0-SNAPSHOT</version>
     <name>inteken-ontvanger-email</name>
     <description>inteken-ontvanger-email</description>
 
     <properties>
-        <java.version>1.8</java.version>
+        <java.version>21</java.version>
     </properties>
 
     <dependencies>
@@ -49,7 +49,7 @@
         <dependency>
             <groupId>com.github.spullara.mustache.java</groupId>
             <artifactId>compiler</artifactId>
-            <version>0.9.6</version>
+            <version>0.9.14</version>
         </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>
@@ -102,18 +102,49 @@
                 <groupId>org.springframework.boot</groupId>
                 <artifactId>spring-boot-maven-plugin</artifactId>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.13.0</version>
+                <configuration>
+                    <release>21</release>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-enforcer-plugin</artifactId>
+                <version>3.5.0</version>
+                <executions>
+                    <execution>
+                        <id>enforce-versions</id>
+                        <goals>
+                            <goal>enforce</goal>
+                        </goals>
+                        <configuration>
+                            <rules>
+                                <requireMavenVersion>
+                                    <version>3.8.4</version>
+                                </requireMavenVersion>
+                                <requireJavaVersion>
+                                    <version>21</version>
+                                </requireJavaVersion>
+                            </rules>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
             <plugin>
                 <groupId>pl.project13.maven</groupId>
                 <artifactId>git-commit-id-plugin</artifactId>
-                <version>4.0.2</version>
+                <version>4.9.10</version>
                 <configuration>
                     <useNativeGit>true</useNativeGit>
                 </configuration>
             </plugin>
             <plugin>
                 <groupId>org.jacoco</groupId>
                 <artifactId>jacoco-maven-plugin</artifactId>
-                <version>0.8.5</version>
+                <version>0.8.12</version>
                 <configuration>
                     <excludes>
                         <exclude>**/*MockMailBox.*</exclude>
@@ -139,7 +170,7 @@
             <extension>
                 <groupId>org.apache.maven.wagon</groupId>
                 <artifactId>wagon-webdav-jackrabbit</artifactId>
-                <version>3.3.4</version>
+                <version>3.5.3</version>
             </extension>
         </extensions>
     </build>