### Description
- It returns status `409 CONFLICT` if there is already a label with same name or a post with same semantic ID.
### Package Changes
_No response_
### Screenshots
_No response_
### Reference
Resolves#133.
### Checklist
- [x] A milestone is set
- [x] The related issuse has been linked to this branch
Reviewed-on: #135
Co-authored-by: SquidSpirit <squid@squidspirit.com>
Co-committed-by: SquidSpirit <squid@squidspirit.com>
