feat: custom newsletter slug

backend/app/core/slug.py

@@ -0,0 +1,18 @@
+import re
+
+
+def sanitize_slug(slug: str | None) -> str | None:
+    """Sanitize a string to be used as a URL slug.
+
+    - Converts to lowercase
+    - Replaces spaces and underscores with hyphens
+    - Removes characters that are not alphanumeric or hyphens
+    - Removes leading/trailing hyphens
+    """
+    if not slug:
+        return None
+    slug = slug.lower()
+    slug = re.sub(r"[\s_]+", "-", slug)
+    slug = re.sub(r"[^a-z0-9-]", "", slug)
+    slug = slug.strip("-")
+    return slug or None