fix: PostgreSQL datetime formatting with `to_char`

[thomas-chauvet]

📑 Description

When using PostgreSQL as backend database an error occur when converting datetime to string with the to_char PostgreSQL function as it expects a specific formatting

✅ Checks

• [x] My pull request adheres to the code style of this project
• [ ] My code requires changes to the documentation
• [ ] I have updated the documentation as required
• [ ] All the tests have passed

ℹ Additional Information

This PR fix a bug that makes unusable the web application. On Providers page, the KPI displaying the number of alerts per integration crashed. Thus, it is impossible to manage integration because of query crashing in the backend.

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