Add support for extra docker arguments referencing machines environment variables using the agent.docker_allow_host_environ configuration option to allow users to also be able to use $ENV in the task's docker arguments

docs/clearml.conf

@@ -185,6 +185,7 @@ agent {
 
     # optional arguments to pass to docker image
     # these are local for this agent and will not be updated in the experiment's docker_cmd section
+    # You can also pass host environments into the container with ["-e", "HOST_NAME=$HOST_NAME"]
     # extra_docker_arguments: ["--ipc=host", "-v", "/mnt/host/data:/mnt/data"]
 
     # optional shell script to run in docker when started before the experiment is started
@@ -195,6 +196,12 @@ agent {
     # change to false to skip installation and decrease docker spin up time
     # docker_install_opencv_libs: true
 
+    # Allow passing host environments into docker container with Task's docker container args
+    # Example "-e HOST_NAME=$HOST_NAME"
+    # NOTICE this might introduce security risk allowing access to keys/secret on the host machine1
+    # Use with care!
+    # docker_allow_host_environ: false
+
     # set to true in order to force "docker pull" before running an experiment using a docker image.
     # This makes sure the docker image is updated.
     docker_force_pull: false