Fix doubled dots in path_and_rename and add a test for it

As os.path.splitext returns the file extension including a dot, adding an extra one is superfluous.

aleksis/core/tests/util/test_core_helpers.py

+import re
+
+from aleksis.core.util.core_helpers import path_and_rename
+
+
+def test_path_and_rename():
+    re_base = r"[a-z0-9]+"
+
+    example_1 = "sdjaasjkl.jpg"
+    re_example_1 = "files/" + re_base + r"\.jpg"
+    re2_example_1 = "images/" + re_base + r"\.jpg"
+    assert re.match(re_example_1, path_and_rename(None, example_1))
+    assert re.match(re2_example_1, path_and_rename(None, example_1, upload_to="images"))
+
+    example_2 = "sdjaasjkl"
+    re_example_2 = "files/" + re_base
+    re2_example_2 = "images/" + re_base
+    assert re.match(re_example_2, path_and_rename(None, example_2))
+    assert re.match(re2_example_2, path_and_rename(None, example_2, upload_to="images"))