Feat/support parent child chunk (#12092)

api/core/entities/knowledge_entities.py

@@ -0,0 +1,19 @@
+from typing import Optional
+
+from pydantic import BaseModel
+
+
+class PreviewDetail(BaseModel):
+    content: str
+    child_chunks: Optional[list[str]] = None
+
+
+class QAPreviewDetail(BaseModel):
+    question: str
+    answer: str
+
+
+class IndexingEstimate(BaseModel):
+    total_segments: int
+    preview: list[PreviewDetail]
+    qa_preview: Optional[list[QAPreviewDetail]] = None