PLT-6262 Add config setting to disable file attachments (#6301)

* Add config setting to disable file attachments

* Add unit tests

* Updating UI for no attachments (#6312)

* Update UI text on file upload System Console setting (#6313)

* Update storage_settings.jsx

* Update en.json

app/file.go

@@ -84,7 +84,7 @@ func ReadFile(path string) ([]byte, *model.AppError) {
 			return f, nil
 		}
 	} else {
-		return nil, model.NewLocAppError("ReadFile", "api.file.read_file.configured.app_error", nil, "")
+		return nil, model.NewAppError("ReadFile", "api.file.read_file.configured.app_error", nil, "", http.StatusNotImplemented)
 	}
 }