Join documentation is out of date

[waza-ari]

Describe the bug or question As far as I can tell, the join documentation is out of date

For example, it shows:

user_tier = await user_crud.get_joined(
    db=db,
    model=Tier,
    join_on=User.tier_id == Tier.id,
    join_type="left",
    join_prefix="tier_",,
    id=1
)

While the code suggests it should be join_model instead of model:

https://github.com/igorbenav/fastcrud/blob/5e45aee16db9b541d98886472618ec967a3c527b/fastcrud/crud/fast_crud.py#L691