fix: markup link button without command

pybotx/models/message/markup.py

@@ -178,7 +178,7 @@ class BotXAPIButtonOptions(UnverifiedPayloadBaseModel):
 
 
 class BotXAPIButton(UnverifiedPayloadBaseModel):
-    command: str
+    command: Missing[str]
     label: str
     data: dict[str, Any]
     opts: BotXAPIButtonOptions

tests/models/test_botx_api_markup.py

@@ -1,11 +1,14 @@
 import json
+import warnings
 from typing import Any
 
 
+from pybotx import BubbleMarkup
 from pybotx.models.message.markup import (
     BotXAPIMarkup,
     BotXAPIButton,
     BotXAPIButtonOptions,
+    api_markup_from_domain,
 )
 
 
@@ -114,3 +117,35 @@ def test_botx_api_markup_jsonable_dict() -> None:
         ]
     ]
     assert jsonable_dict == expected_dict
+
+
+def test_botx_api_markup_link_button_without_command() -> None:
+    # - Arrange -
+    markup = BubbleMarkup()
+    markup.add_button(
+        label="Open me",
+        link="https://example.com",
+    )
+
+    # - Act -
+    with warnings.catch_warnings(record=True) as captured_warnings:
+        warnings.simplefilter("always")
+        jsonable_dict = api_markup_from_domain(markup).jsonable_dict()
+
+    # - Assert -
+    expected_dict: list[list[dict[str, Any]]] = [
+        [
+            {
+                "label": "Open me",
+                "data": {},
+                "opts": {
+                    "silent": True,
+                    "align": "center",
+                    "handler": "client",
+                    "link": "https://example.com",
+                },
+            }
+        ]
+    ]
+    assert jsonable_dict == expected_dict
+    assert not captured_warnings