Add ability to re-cache CMS page URLs

[aligent-lturner]

We should add the ability to re-cache CMS page URLs.

• Must
  • Re-cache URL when the CMS page is updated
• Should
  • Re-cache URL when a block within the page is updated
• Could
  • Re-cache URL when the content of a product widget within the page is updated
  • Re-cache URL when the content of a product widget within a block on the page is updated

[aligent-lturner]

Regarding product widgets - these end up in the CMS page content in the form:

{{widget type="Magento\CatalogWidget\Block\Product\ProductsList" ... condition_option="X" condition_option_value="Y" ... conditions_encoded="Z" ... }}

Where:

• "X" is one of sku, category_ids or condition
• "Y" is either a comma-separated list of skus, a comma-separated list of category ids or empty, depending on the value of X
• "Z" is populated with a list of custom conditions when X is condition

In the case of sku and category_ids conditions, we would be able to use preg_match to extract the skus or category ids that should result in the CMS page being updated. The condition case is much more complicated, and will likely be ignored as part of this issue, but could potentially be added at a later time.