Clicking "Create and expose schema to Data API" fails with error:
<img width="461" height="114" alt="image"
src="https://github.com/user-attachments/assets/0b37c443-2cba-4f4b-8535-c1143801dc72"
/>
The postgrest config can return `db_pool` as null,
but the mutation was passing it directly to the API which expects a
number.
This fix omits `db_pool` from the request body when null,
allowing it to use its default value.
- closes https://github.com/supabase/supabase/issues/41511
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## Summary by CodeRabbit
* **Bug Fixes**
* Improved API settings configuration handling to properly manage
database pool parameters, ensuring more accurate and reliable API schema
mutations.
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settings.</sub>
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