Feat/dify rag (#2528)

Co-authored-by: jyong <jyong@dify.ai>

api/core/rag/cleaner/cleaner_base.py

@@ -0,0 +1,12 @@
+"""Abstract interface for document cleaner implementations."""
+from abc import ABC, abstractmethod
+
+
+class BaseCleaner(ABC):
+    """Interface for clean chunk content.
+    """
+
+    @abstractmethod
+    def clean(self, content: str):
+        raise NotImplementedError
+