import_util: Make build_message only take kwargs.

build_message has a lot of arguments, so it's hard to verify correctness
of callers that just try to get the order right. It's much clearer to be
explicit via kwargs. mattermost.py and rocketchat.py already do this, so
let's bring slack.py and gitter.py up to par.

zerver/data_import/gitter.py

@@ -272,13 +272,13 @@ def convert_gitter_workspace_messages(
             user_id = user_map[get_user_from_message(message)]
             recipient_id = stream_map[message["room"]] if "room" in message else 0
             zulip_message = build_message(
-                topic_name,
-                message_time,
-                message_id,
-                message["text"],
-                rendered_content,
-                user_id,
-                recipient_id,
+                topic_name=topic_name,
+                date_sent=message_time,
+                message_id=message_id,
+                content=message["text"],
+                rendered_content=rendered_content,
+                user_id=user_id,
+                recipient_id=recipient_id,
             )
             zerver_message.append(zulip_message)
 

zerver/data_import/import_util.py

@@ -486,6 +486,7 @@ def build_huddle(huddle_id: int) -> ZerverFieldsT:
 
 
 def build_message(
+    *,
     topic_name: str,
     date_sent: float,
     message_id: int,

zerver/data_import/slack.py

@@ -953,16 +953,16 @@ def channel_message_to_zerver_message(
         topic_name = "imported from Slack"
 
         zulip_message = build_message(
-            topic_name,
-            get_timestamp_from_message(message),
-            message_id,
-            content,
-            rendered_content,
-            slack_user_id_to_zulip_user_id[slack_user_id],
-            recipient_id,
-            has_image,
-            has_link,
-            has_attachment,
+            topic_name=topic_name,
+            date_sent=get_timestamp_from_message(message),
+            message_id=message_id,
+            content=content,
+            rendered_content=rendered_content,
+            user_id=slack_user_id_to_zulip_user_id[slack_user_id],
+            recipient_id=recipient_id,
+            has_image=has_image,
+            has_link=has_link,
+            has_attachment=has_attachment,
         )
         zerver_message.append(zulip_message)