[serve][cli] Handle nested = in serve run arguments (ray-project#…

…49719)

Probably not perfect, but a small patch fix...

Without this:
```
> serve run main:app FOO='abc=def'
Error: Invalid key-value string 'FOO=abc=def'. Must be of the form 'key=value'
```

---------

Signed-off-by: Edward Oakes <ed.nmi.oakes@gmail.com>
Signed-off-by: Puyuan Yao <williamyao034@gmail.com>

python/ray/serve/scripts.py

@@ -111,8 +111,8 @@ def process_dict_for_yaml_dump(data):
 def convert_args_to_dict(args: Tuple[str]) -> Dict[str, str]:
     args_dict = dict()
     for arg in args:
-        split = arg.split("=")
-        if len(split) != 2:
+        split = arg.split("=", maxsplit=1)
+        if len(split) != 2 or len(split[1]) == 0:
             raise click.ClickException(
                 f"Invalid application argument '{arg}', "
                 "must be of the form '<key>=<val>'."

python/ray/serve/tests/unit/test_cli.py

@@ -21,9 +21,15 @@ def test_convert_args_to_dict():
     ):
         convert_args_to_dict(("bad_arg",))
 
-    assert convert_args_to_dict(("key1=val1", "key2=val2")) == {
+    with pytest.raises(
+        click.ClickException, match="Invalid application argument 'bad_arg='"
+    ):
+        convert_args_to_dict(("bad_arg=",))
+
+    assert convert_args_to_dict(("key1=val1", "key2=val2", "key3=nested=val")) == {
         "key1": "val1",
         "key2": "val2",
+        "key3": "nested=val",
     }