Fix bugs (#4241)

### What problem does this PR solve?

1. Refactor error message
2. Fix knowledges are created on ES and can't be found in Infinity. The
document chunk fetch error.

### Type of change

- [x] Fix bug
- [x] Refactoring

---------

Signed-off-by: jinhai <haijin.chn@gmail.com>

api/apps/canvas_app.py

@@ -94,7 +94,7 @@ def getsse(canvas_id):
     token = token[1]
     objs = APIToken.query(beta=token)
     if not objs:
-        return get_data_error_result(message='Token is not valid!"')
+        return get_data_error_result(message='Authentication error: API key is invalid!"')
     e, c = UserCanvasService.get_by_id(canvas_id)
     if not e:
         return get_data_error_result(message="canvas not found.")