Strip trailing periods from topic titles

Note that this will also prevent a title from ending with "...". I did a
search for all titles that ended in that, and none of them seemed
essential (and probably should have been removed), so I think this
should be fine.

tildes/tests/test_title.py

@@ -45,6 +45,13 @@ def test_whitespace_trimmed(title_schema):
     assert result["title"] == "actual title"
 
 
+def test_trailing_periods_trimmed(title_schema):
+    """Ensure trailing periods on a title are removed."""
+    title = "This is an interesting story."
+    result = title_schema.load({"title": title})
+    assert not result["title"].endswith(".")
+
+
 def test_consecutive_whitespace_removed(title_schema):
     """Ensure consecutive whitespace in a title is compressed."""
     title = "sure   are  \n  a  lot    of     spaces"

tildes/tildes/schemas/topic.py

@@ -36,6 +36,18 @@ class TopicSchema(Schema):
     user = Nested(UserSchema, dump_only=True)
     group = Nested(GroupSchema, dump_only=True)
 
+    @pre_load
+    def prepare_title(self, data: dict, many: bool, partial: Any) -> dict:
+        """Prepare the title before it's validated."""
+        # pylint: disable=unused-argument
+        if "title" not in data:
+            return data
+
+        # strip any trailing periods
+        data["title"] = data["title"].rstrip(".")
+
+        return data
+
     @pre_load
     def prepare_tags(self, data: dict, many: bool, partial: Any) -> dict:
         """Prepare the tags before they're validated."""