[Feature]: Add a contains operator for membership

[mitcheaton1]

Problem description

It would be nice to add some more membership operators.

For example, I have auth_roles on a viewer, which is a list of roles (viewer has_many auth_roles). I want to check that :start_discussions role is a member of the viewers auth roles.

permit()
|> permission_to(:start_discussion, Article, viewer: [auth_roles: {:contains, [:start_discussions]}])

Proposed solution

Add an operator like contains to check inside of a list

Alternatives considered

No response

Use case

To use when you are checking an association that is a list for membership

Desired API/code example

permit()
|> permission_to(:start_discussion, Article, viewer: [auth_roles: {:contains, [:start_discussions]}])

Priority (1-5)

1 - Low - Nice to have

Additional Context

No response

Checklist

• I have searched for existing issues before creating this one
• I have checked the roadmap in the README
• This is a feature request, not a bug report or question. For general questions, please use Elixir Slack's Permit channel.

[vincentvanbush]

Valid point, admittedly I haven't put too much thought into supporting array fields with Permit yet. Right now you can work around this by modelling the auth roles as a proper many-to-many association and doing something like:

permit()
|> permission_to(:start_discussion, Article, viewer: [auth_roles: [role_name: :start_discussion]])

Then it gets converted with Permit.Ecto to a join query and it's correct. On the other hand, though, I'm not 100% sure it's going to behave as intended with vanilla Permit or just the scenario of asking for permission (as opposed to conversion to query). I'll look into that as well.

Nonetheless, this operator is a nice idea; it raises the question of what to do with the current inclusion operator when an array field is used. For example, status: ["published", "draft"] means either value for a string (or varchar) field, but for an array field it would mean an exact array.