Orders autosuggest foundations

[JakePT]

Description of the Change

The PR implements the foundations for the orders autosuggest for WooCommerce feature. It includes:

• A class for the Orders sub-feature, this incudes:
  • Creating and saving the search template for the order search API on ElasticPress.io.
  • Retrieving and setting a temporary token for authenticated front-end requests to ElasticPress.io.
  • Loading front-end assets.
• The UI.

The class is not instantiated in the WooCommerce feature, so it can not be currently activated.

Remaining to be implemented, as per #3277, are:

• A new field and ngram that includes the order number, first name, last name, and email address to support partial word matches and highlighting.
• A UI toggle for enabling Orders Autosuggest.
• Logic to index Orders when feature is active, even if Protected Content is disabled.
• Logic to require index when the feature is activated.
• Tests.

How to test the Change

1. Connect to an EP.io environment that supports the order search API.
2. Activate the WooCommerce and Protected Content features.
3. Add ( new Orders() )->setup(); to the setup() method of the WooCommerce feature class.
4. Perform an index.
5. Visit WooCommerce > Orders and start searching for orders. Suggestions should be offered in a listbox below the search form.

Changelog Entry

• Added: Autosuggest for WooCommerce Orders.

Credits

@JakePT

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.

[felipeelia]

@JakePT I left some comments (mostly just thoughts and things we will need to keep track of). Do you mind reaching out to me on slack to share an endpoint I can use to test it? Thanks!

[felipeelia]

We need to delete these during the plugin uninstall. Also, this will eventually expire, right? I didn't find where we are getting a new one if that is the case, sorry :(

[JakePT]

@felipeelia Yeah I'll check with Dustin how we want to do that. At the moment it's treated as if the tokens are permanent.