Chore: Java 21.

.drone.yml

@@ -3,7 +3,7 @@ type: docker
 name: default
 steps:
   - name: build
-    image: maven:3.8-openjdk-18-slim
+    image: maven:3.9-eclipse-temurin-21
     commands:
       - mvn clean install -DskipTests=true -Dmaven.javadoc.skip=true -B -V
     when:
@@ -13,7 +13,7 @@ steps:
           - refs/head/feature/**
           - refs/tags/**
   - name: test
-    image: maven:3.8-openjdk-18-slim
+    image: maven:3.9-eclipse-temurin-21
     commands:
       - mvn test -B
     when:
@@ -22,7 +22,7 @@ steps:
           - master
           - feature/*
   - name: deploy
-    image: maven:3.8-openjdk-18-slim
+    image: maven:3.9-eclipse-temurin-21
     environment:
       REPO_TOKEN:
         from_secret: repo-token