refactor(myscale):Set the default value of the myscale vector db in DifyConfig. (#6441)

api/configs/middleware/vdb/myscale_config.py

-from typing import Optional
 
 from pydantic import BaseModel, Field, PositiveInt
 
     MyScale configs
     """
 
-    MYSCALE_HOST: Optional[str] = Field(
+    MYSCALE_HOST: str = Field(
         description='MyScale host',
-        default=None,
+        default='localhost',
     )
 
-    MYSCALE_PORT: Optional[PositiveInt] = Field(
+    MYSCALE_PORT: PositiveInt = Field(
         description='MyScale port',
         default=8123,
     )
 
-    MYSCALE_USER: Optional[str] = Field(
+    MYSCALE_USER: str = Field(
         description='MyScale user',
-        default=None,
+        default='default',
     )
 
-    MYSCALE_PASSWORD: Optional[str] = Field(
+    MYSCALE_PASSWORD: str = Field(
         description='MyScale password',
-        default=None,
+        default='',
     )
 
-    MYSCALE_DATABASE: Optional[str] = Field(
+    MYSCALE_DATABASE: str = Field(
         description='MyScale database name',
-        default=None,
+        default='default',
     )
 
-    MYSCALE_FTS_PARAMS: Optional[str] = Field(
+    MYSCALE_FTS_PARAMS: str = Field(
         description='MyScale fts index parameters',
-        default=None,
+        default='',
     )

api/core/rag/datasource/vdb/myscale/myscale_vector.py

         return MyScaleVector(
             collection_name=collection_name,
             config=MyScaleConfig(
-                # TODO: I think setting those values as the default config would be a better option.
-                host=dify_config.MYSCALE_HOST or "localhost",
-                port=dify_config.MYSCALE_PORT or 8123,
-                user=dify_config.MYSCALE_USER or "default",
-                password=dify_config.MYSCALE_PASSWORD or "",
-                database=dify_config.MYSCALE_DATABASE or "default",
-                fts_params=dify_config.MYSCALE_FTS_PARAMS or "",
+                host=dify_config.MYSCALE_HOST,
+                port=dify_config.MYSCALE_PORT,
+                user=dify_config.MYSCALE_USER,
+                password=dify_config.MYSCALE_PASSWORD,
+                database=dify_config.MYSCALE_DATABASE,
+                fts_params=dify_config.MYSCALE_FTS_PARAMS,
             ),
         )