Add function to retrieve markers from OAS object

So far the very same logic, the one that retrieves markers out from OAS
object, is implemented two times. Once, for request parameters, and
once, for response headers. Since I'm about to introduce the very same
logic in third place, it's better to move it into helper function.

sphinxcontrib/openapi/renderers/_httpdomain.py

@@ -107,6 +107,26 @@ def _iterexamples(media_types, example_preference, examples_from_schemas):
         yield content_type, example
 
 
+def _get_markers_from_object(oas_object, schema):
+    """Retrieve a bunch of OAS object markers."""
+
+    markers = []
+
+    if schema.get("type"):
+        type_ = schema["type"]
+        if schema.get("format"):
+            type_ = f"{type_}:{schema['format']}"
+        markers.append(type_)
+
+    if oas_object.get("required"):
+        markers.append("required")
+
+    if oas_object.get("deprecated"):
+        markers.append("deprecated")
+
+    return markers
+
+
 class HttpdomainRenderer(abc.RestructuredTextRenderer):
     """Render OpenAPI v3 using `sphinxcontrib-httpdomain` extension."""
 
@@ -229,7 +249,6 @@ def render_parameter(self, parameter):
         kinds = CaseInsensitiveDict(
             {"path": "param", "query": "queryparam", "header": "reqheader"}
         )
-        markers = []
         schema = parameter.get("schema", {})
 
         if "content" in parameter:
@@ -247,25 +266,14 @@ def render_parameter(self, parameter):
             )
             return
 
-        if schema.get("type"):
-            type_ = schema["type"]
-            if schema.get("format"):
-                type_ = f"{type_}:{schema['format']}"
-            markers.append(type_)
-
-        if parameter.get("required"):
-            markers.append("required")
-
-        if parameter.get("deprecated"):
-            markers.append("deprecated")
-
         yield f":{kinds[parameter['in']]} {parameter['name']}:"
 
         if parameter.get("description"):
             yield from indented(
                 self._convert_markup(parameter["description"]).strip().splitlines()
             )
 
+        markers = _get_markers_from_object(parameter, schema)
         if markers:
             markers = ", ".join(markers)
             yield f":{kinds[parameter['in']]}type {parameter['name']}: {markers}"
@@ -342,26 +350,14 @@ def render_response(self, status_code, response):
                         .splitlines()
                     )
 
-                markers = []
                 schema = header_value.get("schema", {})
                 if "content" in header_value:
                     # According to OpenAPI v3 spec, 'content' in this case may
                     # have one and only one entry. Hence casting its values to
                     # list is not expensive and should be acceptable.
                     schema = list(header_value["content"].values())[0].get("schema", {})
 
-                if schema.get("type"):
-                    type_ = schema["type"]
-                    if schema.get("format"):
-                        type_ = f"{type_}:{schema['format']}"
-                    markers.append(type_)
-
-                if header_value.get("required"):
-                    markers.append("required")
-
-                if header_value.get("deprecated"):
-                    markers.append("deprecated")
-
+                markers = _get_markers_from_object(header_value, schema)
                 if markers:
                     markers = ", ".join(markers)
                     yield f":resheadertype {header_name}: {markers}"