Fix: Improve dataset name validation in KB app (#8188)

### What problem does this PR solve?

- Trim whitespace before checking for empty dataset names
- Change length check from >= to > DATASET_NAME_LIMIT for consistency

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

api/apps/kb_app.py

@@ -45,9 +45,9 @@ def create():
     dataset_name = req["name"]
     if not isinstance(dataset_name, str):
         return get_data_error_result(message="Dataset name must be string.")
-    if dataset_name == "":
+    if dataset_name.strip() == "":
         return get_data_error_result(message="Dataset name can't be empty.")
-    if len(dataset_name.encode("utf-8")) >= DATASET_NAME_LIMIT:
+    if len(dataset_name.encode("utf-8")) > DATASET_NAME_LIMIT:
         return get_data_error_result(
             message=f"Dataset name length is {len(dataset_name)} which is large than {DATASET_NAME_LIMIT}")