Add Uuid type and InvalidUuidError type

class InvalidUuidError(ValueError):

    """

    A given string should have been a valid UUID, but was not.

    """

    pass

from uuid import UUID

import sqlalchemy.types as types

from sqlalchemy.engine import Dialect

UUID_LENGTH = 36

class Uuid(types.TypeDecorator):

    """

    A UUID, stored as a 36-character string containing dashes.

    There is a built-in SQLAlchemy type representing a UUID (which uses built-in database types for UUIDs, if they

    exist), but it falls back to 32-character strings (dashes are removed) if there is no such type (like with

    MySQL, MariaDB or SQLite).

    This makes working directly in the database (which often is a requirement) complicated, so we've decided to

    implement our own type for that.

    """

    impl = types.TypeEngine

    cache_ok = True

    def load_dialect_impl(self, dialect: Dialect) -> types.TypeEngine[str]:

        return types.String(UUID_LENGTH)

    def process_bind_param(

        self, value: str | UUID | None, dialect: Dialect

    ) -> str | None:

        if isinstance(value, str):

            # Manually create UUID from string, to raise an error if the string is malformed

            UUID(value)

        return str(value) if value else None

    def process_result_value(self, value: str | None, dialect: Dialect) -> UUID | None:

        return UUID(value) if value else None