Bring base helper from spree_backend

[luisramos0]

What? Why?

Relates to #4050

In this PR we bring the base_helper from spree with a number of generic helper methods used in different parts of the application. See testing notes below for details.

What should we test?

There are couple of different things that need to be validated here.

1. Editing an order, in Customer Details, the placeholder should look like this translated:
   

2. field_container - product edit page looks good and works.

3. error_message_on - editing a product, removing name and saving it will show an error on the top of the page as well as below the name field (can be tested in english):
   

4. preference_field_tag - make sure you can edit preferences in the general settings, for example, verify the footer_tos_url field is working correctly.

5. zones - make sure you can add and remove countries and states from a zone: this needs to be tested for both country based zones and state based zones.

6. preference_fields - make sure you can configure calculators correctly on shipping_methods, payment methods and enterprise fees. everythin shouldd be fine. a quick test of the form is enough.

7. product properties - make sure you can add properties to a product - test the link on the top right to add more lines to the form

8. producer properties - make sure we can add and remove properties from a producer enterprise - this page is currently a bit weird because you can only add more properties by saving the form (it will add one if all are used) but there should be a button on the top "add properties" like in the product properties above. I think we can open a bug for this. Probably S4.

Release notes

Changelog Category: Changed
Brought base_helper with generic helper methods to build the admin pages from spree to make ofn independent of spree.

[lin-d-hop]

Ping @luisramos0 conflicts

[luisramos0]

rebased to resolve conflicts. ready for testing.

[luisramos0]

rebased to resolved conflict on rubocop file.

[RachL]

This is looking good!

My notes: https://docs.google.com/document/d/1vsU8Yqo9XmUVGIJQ_dm7dpdxmdroEMhcsYgH_gI9Mr8/edit#

@luisramos0 I didn't find what you've meant by the footer_tos_url field . So I've tested the shopping preferences entirely. Hope this was the right place 👍

[luisramos0]

hmm, I meant "preferences in the general settings" but you say "shopping preferences".
I mean /admin/general_settings
tos = terms of service - "Conditions d'utilisation URL"
Let me know if you think you have verified this page.
thanks!

[RachL]

@luisramos0 not at all! I didn't know this was called preferences as well. I just tested this page. Looking good!

[luisramos0]

sorry about that, I got taken by the names of the variables. they are all preferences in the code...
thanks!