[Bug] in is allowed operator for array field but does not filter for list values

[Techn1x]

Summary / Steps to reproduce

I've got a flop schema like this, with a field that is a string array

@derive {
    Flop.Schema,
    filterable: [
      :subscription_types
    ],
    ...

schema "school_classes" do
    field :subscription_types, {:array, :string}

Flop tells me that in is an allowed operator

iex(8)> Flop.Filter.allowed_operators(SchoolClass, :subscription_types)
[:==, :!=, :empty, :not_empty, :<=, :<, :>=, :>, :in, :not_in, :contains, :not_contains]

So I construct a filter like this, to filter records to only those that have reading or maths in their subscription_types. Flop tells me this filter is valid

iex(8)> Flop.validate(%{ filters: [%{ field: :subscription_types, op: :in, value: ["reading", "maths"] }] })
{:ok, %Flop{ ... }

But when I apply it, Flop tells me its invalid

Flop.validate_and_run(
  query,
  %{ filters: [%{ field: :subscription_types, op: :in, value: ["reading", "maths"] }] },
  for: SchoolClass
)

Invalid Flop: #Ecto.Changeset<action: :replace, changes: %{filters: [#Ecto.Changeset<action: :insert, changes: %{op: :in, field: :subscription_types}, errors: [value: {"is invalid", []}], data: #Flop.Filter<>, valid?: false, ...>], limit: 50, order_by: [:name], order_directions: [:asc]}, errors: [], data: #Flop<>, valid?: false, ...>

Is this expected or am I doing something wrong? If it's not supposed to work, should in be removed from the allowed operators? and/or is there a combination of filters that will allow me to achieve this with Flop filters?

Elixir/Flop/Ecto Version Info

click to expand

Erlang/OTP 26 [erts-14.2.2] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [jit]

Elixir 1.17.1 (compiled with Erlang/OTP 25)

• ecto 3.12.5 (Hex package) (mix)
• ecto_sql 3.12.1 (Hex package) (mix)
  locked at 3.12.1 (ecto_sql) aff5b958
• flop 0.26.1 (Hex package) (mix)
  locked at 0.26.1 (flop) 5fcab8a1
• flop_phoenix 0.23.1 (Hex package) (mix)
  locked at 0.23.1 (flop_phoenix) e7d55a2e

[Techn1x]

I'm somewhat confident that this is a bug since no reason is given for the invalid filter error
errors: [value: {"is invalid", []}]

whereas other mistakes tend to give a reason there

[Techn1x]

As a plan B I would write it as a "custom_field", though I receive the same error. in operator only accepts lists as a value, yet when I provide a list it errors. I am guessing this is to do with providing ecto_type: {:array, :string}, in the custom field schema, it ends up treated the same way and we hit the same bug