Enhancement: Add not_found custom error message

[noamsto]

Summary

When doing repository.get() there is an option to set custom message when various error occur, but there is no option for NotFoundError.
It will be very convenient if this will be added.

Basic Example

        org = await organizations_service.get_one_or_none(Organization.id == organization_id)
        if not org:
            raise NotFoundException("Organization not found")

The above will become:

        org = await organizations_service.get(
            organization_id, error_messages=ErrorMessages(not_found="Organization not found")
        )

Drawbacks and Impact

No response

Unresolved questions

No response