Feature: Enhanced templating for filename format (#7836)

Co-authored-by: shamoon <4887959+shamoon@users.noreply.github.com>

src/documents/templating/utils.py

@@ -0,0 +1,24 @@
+import re
+
+
+def convert_format_str_to_template_format(old_format: str) -> str:
+    """
+    Converts old Python string format (with {}) to Jinja2 template style (with {{ }}),
+    while ignoring existing {{ ... }} placeholders.
+
+    :param old_format: The old style format string (e.g., "{title} by {author}")
+    :return: Converted string in Django Template style (e.g., "{{ title }} by {{ author }}")
+    """
+
+    # Step 1: Match placeholders with single curly braces but not those with double braces
+    pattern = r"(?<!\{)\{(\w*)\}(?!\})"  # Matches {var} but not {{var}}
+
+    # Step 2: Replace the placeholders with {{ var }} or {{ }}
+    def replace_with_django(match):
+        variable = match.group(1)  # The variable inside the braces
+        return f"{{{{ {variable} }}}}"  # Convert to {{ variable }}
+
+    # Apply the substitution
+    converted_format = re.sub(pattern, replace_with_django, old_format)
+
+    return converted_format