Storage: Support the s3, azure blob as the object storage of ragflow. (#2278)

### What problem does this PR solve?

issue: https://github.com/infiniflow/ragflow/issues/2277

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

rag/utils/storage_factory.py

@@ -0,0 +1,30 @@
+import os
+from enum import Enum
+
+from rag.utils.azure_sas_conn import RAGFlowAzureSasBlob
+from rag.utils.azure_spn_conn import RAGFlowAzureSpnBlob
+from rag.utils.minio_conn import RAGFlowMinio
+from rag.utils.s3_conn import RAGFlowS3
+
+
+class Storage(Enum):
+    MINIO = 1
+    AZURE_SPN = 2
+    AZURE_SAS = 3
+    AWS_S3 = 4
+
+
+class StorageFactory:
+    storage_mapping = {
+        Storage.MINIO: RAGFlowMinio,
+        Storage.AZURE_SPN: RAGFlowAzureSpnBlob,
+        Storage.AZURE_SAS: RAGFlowAzureSasBlob,
+        Storage.AWS_S3: RAGFlowS3,
+    }
+
+    @classmethod
+    def create(cls, storage: Storage):
+        return cls.storage_mapping[storage]()
+
+
+STORAGE_IMPL = StorageFactory.create(Storage[os.getenv('STORAGE_IMPL', 'MINIO')])