Add JaCoCo for test coverage and update Drone CI settings

Integrate JaCoCo to enforce and report test coverage with a minimum threshold of 65%. Update Drone CI configuration to use a new Docker registry (rubble.se:5000) and add support for authentication with secrets.

.drone.yml

@@ -16,12 +16,16 @@ steps:
   - name: build-image
     image: plugins/docker
     settings:
-      registry: registry.local:5000
-      repo: registry.local:5000/hemhub/api
+      registry: rubble.se:5000
+      repo: rubble.se:5000/hemhub/api
       tags:
         - ${DRONE_BRANCH/\//-}-${DRONE_COMMIT_SHA:0:7}
         - latest
       dockerfile: Dockerfile
+      username:
+        from_secret: docker_username
+      password:
+        from_secret: docker_password
     when:
       branch:
         include: [ main, develop ]
@@ -31,11 +35,15 @@ steps:
   - name: publish-tag
     image: plugins/docker
     settings:
-      registry: registry.local:5000
-      repo: registry.local:5000/hemhub/api
+      registry: rubble.se:5000
+      repo: rubble.se:5000/hemhub/api
       tags:
         - ${DRONE_TAG}
       dockerfile: Dockerfile
+      username:
+        from_secret: docker_username
+      password:
+        from_secret: docker_password
     when:
       event:
         include: [ tag ]