Add show actions for note, artist, artist commentary versions.

Add these endpoints:

* /note_versions/1234
* /artist_versions/1234
* /artist_commentary_versions/1234

This is so the /ip_addresses listing can link to these endpoints.

test/functional/artist_commentary_versions_controller_test.rb

@@ -2,14 +2,11 @@ require 'test_helper'
 
 class ArtistCommentaryVersionsControllerTest < ActionDispatch::IntegrationTest
   context "The artist commentary versions controller" do
-  	setup do
-      @user = FactoryBot.create(:user)
-
-      as_user do
-        @commentary1 = FactoryBot.create(:artist_commentary)
-        @commentary2 = FactoryBot.create(:artist_commentary)
-      end
-  	end
+    setup do
+      @user = create(:user)
+      @commentary1 = as(@user) { create(:artist_commentary) }
+      @commentary2 = as(@user) { create(:artist_commentary) }
+    end
 
     context "index action" do
       should "render" do
@@ -17,5 +14,15 @@ class ArtistCommentaryVersionsControllerTest < ActionDispatch::IntegrationTest
         assert_response :success
       end
     end
+
+    context "show action" do
+      should "work" do
+        get artist_commentary_version_path(@commentary1.versions.first)
+        assert_redirected_to artist_commentary_versions_path(search: { post_id: @commentary1.post_id })
+
+        get artist_commentary_version_path(@commentary1.versions.first), as: :json
+        assert_response :success
+      end
+    end
   end
 end