Allow custom file extensions for directory journal

tests/bdd/features/file_storage.feature

@@ -10,6 +10,13 @@ Feature: Journals iteracting with the file system in a way that users can see
         And the journal directory should contain
             2013/07/23.txt
 
+    Scenario: Adding entries to a Folder journal with a custom extension should generate date files
+        Given we use the config "empty_folder_with_extension.yaml"
+        When we run "jrnl 23 July 2013: Testing folder journal."
+        Then we should get no error
+        And the journal directory should contain
+            2013/07/23.md
+
     Scenario: Adding multiple entries to a Folder journal should generate multiple date files
         Given we use the config "empty_folder.yaml"
         When we run "jrnl 23 July 2013: Testing folder journal."

tests/data/configs/empty_folder_with_extension.yaml

@@ -0,0 +1,13 @@
+default_hour: 9
+default_minute: 0
+editor: ''
+template: false
+encrypt: false
+extension: .md
+highlight: true
+journals:
+  default: features/journals/empty_folder_with_extension/
+linewrap: 80
+tagsymbols: '@'
+timeformat: '%Y-%m-%d %H:%M'
+indent_character: "|"

tests/unit/test_journals_folder_journal.py

@@ -51,7 +51,7 @@ def test_get_day_files_expected_filtering(inputs_and_outputs):
         mock.patch("pathlib.Path.glob", return_value=glob_files),
         mock.patch.object(pathlib.Path, "is_file", return_value=True),
     ):
-        actual_output = list(Folder._get_day_files(year_month_path))
+        actual_output = list(Folder._get_day_files(year_month_path, ".txt"))
         actual_output.sort()
 
         expected_output.sort()