make send-request and compute accept plain json

this MR make the send-request and compute commands accept plain yaml or json data, i.e. you can now do something like

python -m my_backend_module compute '{func_name: "version_info"}'

and

python -m my_backend_module send-request '{func_name: "version_info"}'

as well as

python -m my_backend_module send-request some_request_in_a_file.yaml
python -m my_backend_module compute some_request_in_a_file.yaml

demessaging/cli.py

@@ -479,12 +479,15 @@ def get_parser(
     # test subparser (to test the connection to the connect to the pulsar
     # messaging system)
     sp = subparsers.add_parser(
-        "send-request", help="Test a request via the pulsar messaging system."
+        "send-request", help="Test a request via the messaging system."
     )
     sp.add_argument(
         "request",
-        help="A JSON-formatted file with the request.",
-        type=argparse.FileType("r"),
+        help=(
+            "The request to send as YAML string, or the path to a YAML or "
+            "JSON file."
+        ),
+        type=_load_dict,
     )
     sp.set_defaults(method_name="send_request", command_params=["request"])
 
@@ -495,8 +498,11 @@ def get_parser(
     )
     sp.add_argument(
         "request",
-        help="A JSON-formatted file with the request.",
-        type=argparse.FileType("r"),
+        help=(
+            "The request to process as YAML string, or the path to a YAML or "
+            "JSON file."
+        ),
+        type=_load_dict,
     )
     sp.set_defaults(method_name="process_request", command_params=["request"])