Improve storage engine (#4341)

### What problem does this PR solve?

- Bring `STORAGE_IMPL` back in `rag/svr/cache_file_svr.py`
- Simplify storage connection when working with AWS S3

### Type of change

- [x] Refactoring

conf/service_conf.yaml

   db_name: 'default_db'
 redis:
   db: 1
-  password: 'infini_rag_flow' 
+  password: 'infini_rag_flow'
   host: 'redis:6379'
 
 # postgres:
 #   max_connections: 100
 #   stale_timeout: 30
 # s3:
-#   endpoint: 'endpoint'
 #   access_key: 'access_key'
 #   secret_key: 'secret_key'
 #   region: 'region'

docker/service_conf.yaml.template

   db_name: 'default_db'
 redis:
   db: 1
-  password: '${REDIS_PASSWORD:-infini_rag_flow}' 
+  password: '${REDIS_PASSWORD:-infini_rag_flow}'
   host: '${REDIS_HOST:-redis}:6379'
 
 # postgres:
 #   max_connections: 100
 #   stale_timeout: 30
 # s3:
-#   endpoint: 'endpoint'
 #   access_key: 'access_key'
 #   secret_key: 'secret_key'
 #   region: 'region'

rag/svr/cache_file_svr.py

 
 from api.db.db_models import close_connection
 from api.db.services.task_service import TaskService
-from rag.utils.minio_conn import MINIOs
+from rag.utils.storage_factory import STORAGE_IMPL
 from rag.utils.redis_conn import REDIS_CONN
 
 
                     key = "{}/{}".format(kb_id, loc)
                     if REDIS_CONN.exist(key):
                         continue
-                    file_bin = MINIOs.get(kb_id, loc)
+                    file_bin = STORAGE_IMPL.get(kb_id, loc)
                     REDIS_CONN.transaction(key, file_bin, 12 * 60)
                     logging.info("CACHE: {}".format(loc))
                 except Exception as e:

rag/utils/s3_conn.py

 import logging
 import boto3
 from botocore.exceptions import ClientError
-from botocore.client import Config
 import time
 from io import BytesIO
 from rag.utils import singleton
     def __init__(self):
         self.conn = None
         self.s3_config = settings.S3
-        self.endpoint = self.s3_config.get('endpoint', None)
         self.access_key = self.s3_config.get('access_key', None)
         self.secret_key = self.s3_config.get('secret_key', None)
         self.region = self.s3_config.get('region', None)
             pass
 
         try:
-
-            config = Config(
-                s3={
-                    'addressing_style': 'virtual'
-                }
-            )
-
             self.conn = boto3.client(
                 's3',
-                endpoint_url=self.endpoint,
                 region_name=self.region,
                 aws_access_key_id=self.access_key,
-                aws_secret_access_key=self.secret_key,
-                config=config
+                aws_secret_access_key=self.secret_key
             )
         except Exception:
-            logging.exception(
-                "Fail to connect %s" % self.endpoint)
+            logging.exception(f"Fail to connect at region {self.region}")
 
     def __close__(self):
         del self.conn