Deprecate PowerConverter based to_sipity_action

`PowerConverter` is a community-maintained gem, but is not in the Samvera
namespace. Depending on it under these circumstances is not in keeping with our
policy.

Rather than simply inline the `PowerConverter` class, this proposes pushing in
the direction a more generic ruby pattern that inspired
it. http://devblog.avdi.org/2012/05/07/a-ruby-conversion-idiom/

app/conversions/power_converters/sipity_action.rb

@@ -1,4 +1,5 @@
 PowerConverter.define_conversion_for(:sipity_action) do |input, scope|
+  Deprecation.warn('PowerConverter is deprecated. Use `Sipity::WorkflowAction(input, workflow)` instead')
   workflow_id = PowerConverter.convert_to_sipity_workflow_id(scope)
   case input
   when Sipity::WorkflowAction

app/forms/hyrax/forms/workflow_action_form.rb

@@ -50,9 +50,15 @@ def authorized_for_processing
 
       private
 
+        class << self
+          def workflow_action_for(name, scope:)
+            Sipity::WorkflowAction(name, scope) { nil }
+          end
+        end
+
         def convert_to_sipity_objects!
           @subject = WorkflowActionInfo.new(work, current_user)
-          @sipity_workflow_action = PowerConverter.convert_to_sipity_action(name, scope: subject.entity.workflow) { nil }
+          @sipity_workflow_action = self.class.workflow_action_for(name, scope: subject.entity.workflow)
         end
 
         attr_reader :subject, :sipity_workflow_action

app/models/sipity.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+# rubocop:disable Style/RaiseArgs
+module Sipity
+  ##
+  # Cast an object to a WorkflowAction in a given workflow
+  def WorkflowAction(input, workflow) # rubocop:disable Naming/MethodName
+    workflow_id = PowerConverter.convert_to_sipity_workflow_id(workflow)
+
+    result = case input
+             when WorkflowAction
+               input if input.workflow_id == workflow_id
+             when String, Symbol
+               WorkflowAction.find_by(workflow_id: workflow_id, name: input.to_s)
+             end
+
+    result ||= input.try(:to_sipity_action)
+    return result unless result.nil?
+    return yield if block_given?
+
+    raise ConversionError.new(input)
+  end
+  module_function :WorkflowAction
+
+  # rubocop:enable Style/RaiseArgs
+  class ConversionError < PowerConverter::ConversionError
+    def initialize(value, **options)
+      options[:scope] ||= nil
+      options[:to]    ||= nil
+      super(value, options)
+    end
+  end
+end

app/services/hyrax/workflow/notification_generator.rb

@@ -57,7 +57,7 @@ def assign_scope_and_reason_to(notification:)
         attr_reader :scope
 
         def assign_scope!
-          @scope = PowerConverter.convert_to_sipity_action(notification_configuration.scope, scope: workflow)
+          @scope = Sipity::WorkflowAction(notification_configuration.scope, workflow)
         end
     end
   end

spec/forms/hyrax/forms/workflow_action_form_spec.rb

@@ -20,7 +20,7 @@
 
   context 'if the given user cannot perform the given action' do
     before do
-      allow(PowerConverter).to receive(:convert_to_sipity_action).with('an_action', scope: sipity_entity.workflow).and_return(an_action)
+      allow(described_class).to receive(:workflow_action_for).with('an_action', scope: sipity_entity.workflow).and_return(an_action)
       expect(Hyrax::Workflow::PermissionQuery).to receive(:authorized_for_processing?).and_return(false)
     end
 
@@ -53,7 +53,7 @@
 
   context 'if the given user can perform the given action' do
     before do
-      allow(PowerConverter).to receive(:convert_to_sipity_action).with('an_action', scope: sipity_entity.workflow).and_return(an_action)
+      allow(described_class).to receive(:workflow_action_for).with('an_action', scope: sipity_entity.workflow).and_return(an_action)
       expect(Hyrax::Workflow::PermissionQuery).to receive(:authorized_for_processing?)
         .and_return(true)
     end

spec/models/sipity_spec.rb

@@ -0,0 +1,43 @@
+RSpec.describe Sipity do
+  describe '.WorkflowAction' do
+    let(:workflow_id) { 1 }
+    let(:action) { Sipity::WorkflowAction.new(id: 4, name: 'show', workflow_id: workflow_id) }
+
+    context "with workflow_id and action's workflow_id matching" do
+      it 'will return the object if it is a Sipity::WorkflowAction' do
+        expect(described_class.WorkflowAction(action, workflow_id)).to eq(action)
+      end
+
+      it 'will return the object if it responds to #to_sipity_action' do
+        object = double(to_sipity_action: action)
+        expect(described_class.WorkflowAction(object, workflow_id)).to eq(action)
+      end
+
+      it 'will raise an error if it cannot convert the object' do
+        object = double
+        expect { described_class.WorkflowAction(object, workflow_id) }
+          .to raise_error(Sipity::ConversionError)
+      end
+
+      it 'will use a found action based on the given string and workflow_id' do
+        expect(Sipity::WorkflowAction).to receive(:find_by).and_return(action)
+        expect(described_class.WorkflowAction(action.name, workflow_id)).to eq(action)
+      end
+
+      context "when the WorkflowAction can not be found" do
+        it 'will raise an error' do
+          expect(Sipity::WorkflowAction).to receive(:find_by).and_return(nil)
+          expect { described_class.WorkflowAction(action.name, workflow_id) }
+            .to raise_error(Sipity::ConversionError)
+        end
+      end
+    end
+
+    context "with mismatching workflow_id and action's workflow_id" do
+      it "will fail an error if the scope's workflow_id is different than the actions" do
+        expect { described_class.WorkflowAction(action, workflow_id + 1) }
+          .to raise_error(Sipity::ConversionError)
+      end
+    end
+  end
+end

spec/services/hyrax/workflow/permission_query_spec.rb

@@ -26,7 +26,7 @@ module Workflow
       before { Hyrax::Workflow::WorkflowImporter.generate_from_hash(data: workflow_config, permission_template: sipity_workflow.permission_template) }
 
       def expect_actions_for(user:, entity:, actions:)
-        actions = Array.wrap(actions).map { |action| PowerConverter.convert_to_sipity_action(action, scope: entity.workflow) }
+        actions = Array.wrap(actions).map { |action| Sipity::WorkflowAction(action, entity.workflow) }
         expect(described_class.scope_permitted_workflow_actions_available_for_current_state(user: user, entity: entity)).to eq(actions)
       end