Fix: change create dataset htto api delimiter default value to r'\n' (#7434)
### What problem does this PR solve?
change create dataset delimiter default value to r'\n'
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Remove unnecessary parameter restrictions in dataset creation API
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
Refa: http API create dataset and test cases (#7393)
### What problem does this PR solve?
This PR introduces Pydantic-based validation for the create dataset HTTP
API, improving code clarity and robustness. Key changes include:
1. Pydantic Validation
2. Error Handling
3. Test Updates
4. Documentation
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] Documentation Update
- [x] Refactoring
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