Refactor environment variable configuration in Drone CI

.drone.yml

@@ -5,12 +5,6 @@ name: default
 node_selector:
   physical-node: dev1
 
-env:
-  DOCKER_USERNAME:
-    from_secret: dockerhub-username
-  DOCKER_PASSWORD:
-    from_secret: dockerhub-password
-
 trigger:
   branch:
     - main
@@ -39,7 +33,11 @@ steps:
       build_args_from_env:
         - DOCKER_USERNAME
         - DOCKER_PASSWORD
-
+    environment:
+      DOCKER_USERNAME:
+        from_secret: dockerhub-username
+      DOCKER_PASSWORD:
+        from_secret: dockerhub-password
 
   - name: pull image to dockerhub
     image: docker.io/owncloudci/drone-docker-buildx:4
@@ -57,4 +55,9 @@ steps:
         - linux/arm64
       build_args_from_env:
         - DOCKER_USERNAME
-        - DOCKER_PASSWORD
+        - DOCKER_PASSWORD
+    environment:
+      DOCKER_USERNAME:
+        from_secret: dockerhub-username
+      DOCKER_PASSWORD:
+        from_secret: dockerhub-password