Constraints defined within Meta are not applied when performing data migrations.

Describe the bug
Constraints are defined in the Meta class of the data model, and the native Tortoise migration tool is used to perform data migration. However, the constraints are not created as expected in the resulting database table.

To Reproduce

class Like(Model):
    id = IntField(primary_key=True)
    types = CharField(default='news', max_length=10)
    user_id = IntField(default=0)
    art_id = IntField(default=0) 
    class Meta:
        table = 'like'
        constraints = [UniqueConstraint(fields=('types', 'user_id', 'art_id'),  name='unique_like')]

*The Tortoise‑ORM version is 1.1.8
Expected behavior
A unique index named unique_like was supposed to be created in the database, but nothing appears in the database.
There are no exceptions or error hints during data migration.

Start with the native Tortoise migration tool's handling of constraints declared in a model's Meta class, using the Like model and its unique_like constraint as the reproduction. Run a data migration against the supported database setup and verify that the resulting like table contains the expected unique index without errors.