feat: Indicator to notify of pending product changes not yet published to catalog

[kieckhafer]

Resolves #4281
Impact: minor
Type: feature

Issue

With the removal of revisions, we no long have a way to know if product data has been published to the Catalog, or if the Product collection contains updated data that has not been published.

Solution

On the PDP, we create a hash of the current data on the page, using the same functions created in #4264. We then compare this new hash to the hash saved on the product object (also created in #4264). If the hashes match, the data is consistent between the two collections. If the hashes do not match, it means there are changes waiting to be published, and we display an indicator on the Publish button.

Breaking changes

None.

Testing

1. Create a new product
2. Publish this product to the catalog
3. Update the title (or any field that is published to the catalog)
4. See the indicator appear on the Publish button
5. Press the publish button
6. See the icon change to a "loading" type indicator while the server publishes the changes
7. See the indicator go away

[nnnnat]

Looking good!

[spencern]

This is great! Nice work @kieckhafer

@nnnnat I'm def stealing that gif for the release notes.