chore: extract retrival method literal values into enum (#5060)

api/core/rag/retrieval/retrival_methods.py

@@ -0,0 +1,15 @@
+from enum import Enum
+
+
+class RetrievalMethod(str, Enum):
+    SEMANTIC_SEARCH = 'semantic_search'
+    FULL_TEXT_SEARCH = 'full_text_search'
+    HYBRID_SEARCH = 'hybrid_search'
+
+    @staticmethod
+    def is_support_semantic_search(retrieval_method: str) -> bool:
+        return retrieval_method in {RetrievalMethod.SEMANTIC_SEARCH, RetrievalMethod.HYBRID_SEARCH}
+
+    @staticmethod
+    def is_support_fulltext_search(retrieval_method: str) -> bool:
+        return retrieval_method in {RetrievalMethod.FULL_TEXT_SEARCH, RetrievalMethod.HYBRID_SEARCH}