Add missing admin filter and fix model indexes

[duilio]

Hello,

this PR actually makes two changes:

• add the missing EmptyFieldListFilter.
• fix the model Index class which also accepts positional parameters.

I am not sure if this is the right way to contribute to this repository.

• Is it ok to submit both changes in a single PR?
• How can I be sure everything is working fine? (a.k.a. tests)

[duilio]

I guess CI is not working due to this: https://circleci.com/blog/january-4-2023-security-alert/

[sbdchd]

ugh circle CI is broken

in terms of tests there are some in https://github.com/sbdchd/django-types/blob/72b6ec53b507ebf2a5290829c11c934d432104ec/tests/trout/models.py#L356-L364 where we essentially write some functions that expect a given type and type error if they get something else

[duilio]

@sbdchd in the meantime I've added some tests. I had to push some other changes due to black formatting.

[sbdchd]

Okay I did what circleci said to do, logout and in again so maybe that's fixed it

can you push another commit?

it can be empty I think

git commit -m "fix ci" --allow-empty

[duilio]

@sbdchd unfortunately it doesn't seem to work yet.. :-( same message about oauth.