slack_import: Import Slackbot as a bot instead of a user.

Slackbot should be correctly marked as a bot rather than a regular user
- otherwise, it confusingly appears on the Users list and in the realm
creation from Slack import flow, in the dropdown for choosing the
organization owner account.

Closes #34649

zerver/data_import/slack.py

@@ -333,6 +333,15 @@ def users_to_zerver_userprofile(
                 zerver_customprofilefield_values,
             )
 
+        if is_slackbot(user):
+            is_bot = True
+        else:
+            is_bot = user.get("is_bot", False)
+        if is_bot:
+            bot_type = 1
+        else:
+            bot_type = None
+
         userprofile = UserProfile(
             full_name=get_user_full_name(user),
             is_active=not user.get("deleted", False) and not user["is_mirror_dummy"],
@@ -341,9 +350,9 @@ def users_to_zerver_userprofile(
             email=email,
             delivery_email=email,
             avatar_source=avatar_source,
-            is_bot=user.get("is_bot", False),
+            is_bot=is_bot,
             role=role,
-            bot_type=1 if user.get("is_bot", False) else None,
+            bot_type=bot_type,
             date_joined=timestamp,
             timezone=timezone,
             last_login=timestamp,
@@ -452,6 +461,10 @@ def process_customprofilefields(
                 break
 
 
+def is_slackbot(user: ZerverFieldsT) -> bool:
+    return get_user_full_name(user).lower() == "slackbot"
+
+
 def get_user_email(user: ZerverFieldsT, domain_name: str) -> str:
     if "email" in user["profile"]:
         return user["profile"]["email"]
@@ -459,7 +472,7 @@ def get_user_email(user: ZerverFieldsT, domain_name: str) -> str:
         return Address(username=user["name"], domain=f"{user['team_domain']}.slack.com").addr_spec
     if "bot_id" in user["profile"]:
         return SlackBotEmail.get_email(user["profile"], domain_name)
-    if get_user_full_name(user).lower() == "slackbot":
+    if is_slackbot(user):
         return Address(username="imported-slackbot-bot", domain=domain_name).addr_spec
     raise AssertionError(f"Could not find email address for Slack user {user}")