nixos/windmill: Add module test

nixos/tests/windmill/python3.script

@@ -0,0 +1,39 @@
+# WARN; Cannot download dependency modules from internet during sandbox testing!
+
+import os
+# import wmill
+
+def main(
+    no_default: str,
+    #db: postgresql,
+    name="my friend",
+    age=42,
+    obj: dict = {"even": "dicts"},
+    l: list = ["or", "lists!"],
+    file_: bytes = bytes(0),
+):
+
+    print(f"Hello World and a warm welcome especially to {name}")
+    print("and its acolytes..", age, obj, l, len(file_))
+
+    # retrieve variables, resources, states using the wmill client
+    try:
+        secret = wmill.get_variable("f/examples/secret")
+    except:
+        secret = "No secret yet at f/examples/secret !"
+    print(f"The variable at `f/examples/secret`: {secret}")
+
+    try:
+        # Get last state of this script execution by the same trigger/user
+        last_state = wmill.get_state()
+        new_state = {"foo": 42} if last_state is None else last_state
+        new_state["foo"] += 1
+        wmill.set_state(new_state)
+    except:
+        new_state = {"foo": 43}
+
+    # fetch context variables
+    user = os.environ.get("WM_USERNAME")
+
+    # return value is converted to JSON
+    return {"splitted": name.split(), "user": user, "state": new_state}