Add actionable by filter

This adds a new filter class for the actionable by field.

app/lib/filters/actionable_by.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+class Filters::ActionableBy < Filters::Base
+  def apply
+    return scope if actionable_by.empty?
+
+    scope.where(actionable_by:)
+  end
+
+  def actionable_by
+    Array(params[:actionable_by]).compact_blank
+  end
+end

spec/lib/filters/actionable_by_spec.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+RSpec.describe Filters::ActionableBy do
+  subject(:filtered_scope) { described_class.apply(scope:, params:) }
+
+  context "the params include a actionable_by" do
+    let(:params) { { actionable_by: "assessor" } }
+    let(:scope) { ApplicationForm.all }
+
+    let!(:included) { create(:application_form, :actionable_by_assessor) }
+    let!(:excluded) { create(:application_form, :actionable_by_admin) }
+
+    it { is_expected.to contain_exactly(included) }
+  end
+
+  context "the params include multiple actionable_by" do
+    let(:params) { { actionable_by: %w[assessor nobody] } }
+    let(:scope) { ApplicationForm.all }
+
+    let!(:included) { create(:application_form, :actionable_by_assessor) }
+    let!(:excluded) { create(:application_form, :actionable_by_admin) }
+
+    it { is_expected.to contain_exactly(included) }
+  end
+
+  context "the params don't include reference" do
+    let(:params) { {} }
+    let(:scope) { double }
+
+    it { is_expected.to eq(scope) }
+  end
+end