refactor: Extract `RESOLVED_TOPIC_PREFIX` in topic.py.

This is a prep commit for #18990.

zerver/lib/actions.py

@@ -158,6 +158,7 @@ from zerver.lib.timezone import canonicalize_timezone
 from zerver.lib.topic import (
     LEGACY_PREV_TOPIC,
     ORIG_TOPIC,
+    RESOLVED_TOPIC_PREFIX,
     TOPIC_LINKS,
     TOPIC_NAME,
     filter_by_exact_message_topic,
@@ -5697,9 +5698,6 @@ class MessageUpdateUserInfoResult(TypedDict):
     mention_user_ids: Set[int]
 
 
-RESOLVED_TOPIC_PREFIX = "✔ "
-
-
 def maybe_send_resolve_topic_notifications(
     *,
     user_profile: UserProfile,

zerver/lib/topic.py

@@ -16,6 +16,9 @@ TOPIC_NAME = "subject"
 TOPIC_LINKS = "topic_links"
 MATCH_TOPIC = "match_subject"
 
+# Prefix use to mark topic as resolved.
+RESOLVED_TOPIC_PREFIX = "✔ "
+
 # This constant is actually embedded into
 # the JSON data for message edit history,
 # so we'll always need to handle legacy data

zerver/tests/test_message_edit.py

@@ -9,7 +9,6 @@ from django.http import HttpResponse
 from django.utils.timezone import now as timezone_now
 
 from zerver.lib.actions import (
-    RESOLVED_TOPIC_PREFIX,
     do_change_stream_post_policy,
     do_change_user_role,
     do_delete_messages,
@@ -21,7 +20,7 @@ from zerver.lib.actions import (
 from zerver.lib.message import MessageDict, has_message_access, messages_for_ids
 from zerver.lib.test_classes import ZulipTestCase
 from zerver.lib.test_helpers import cache_tries_captured, queries_captured
-from zerver.lib.topic import LEGACY_PREV_TOPIC, TOPIC_NAME
+from zerver.lib.topic import LEGACY_PREV_TOPIC, RESOLVED_TOPIC_PREFIX, TOPIC_NAME
 from zerver.models import Message, Realm, Stream, UserMessage, UserProfile, get_realm, get_stream