Added external script for fed_job API (NVIDIA#2623)

* Added external script for fed_job API.

* enforce must deploy a controller or executor before adding external script.

---------

Co-authored-by: Yuan-Ting Hsieh (謝沅廷) <yuantingh@nvidia.com>

nvflare/job_config/fed_job.py

@@ -161,6 +161,13 @@ def to(
                 else:
                     print(f"{target} already set to use GPU {self._gpus[target]}. Ignoring gpu={gpu}.")
             self._deploy_map[target].add_executor(obj, tasks=tasks)
+        elif isinstance(obj, str):  # treat the str type object as external script
+            if target not in self._deploy_map:
+                raise ValueError(
+                    f"{target} doesn't have a `Controller` or `Executor`. Deploy one first before adding external script!"
+                )
+
+            self._deploy_map[target].add_external_scripts([obj])
         else:  # handle objects that are not Controller or Executor type
             if target not in self._deploy_map:
                 raise ValueError(
@@ -214,8 +221,9 @@ def _add_referenced_components(self, base_component, target):
             parameters = get_component_init_parameters(base_component)
             attrs = base_component.__dict__
             for param in parameters:
-                if param in attrs:
-                    base_id = attrs[param]
+                attr_key = param if param in attrs.keys() else "_" + param
+                if attr_key in attrs.keys():
+                    base_id = attrs[attr_key]
                     if isinstance(base_id, str):  # could be id
                         if base_id in self._components:
                             self._deploy_map[target].add_component(self._components[base_id], base_id)