[Dawn] How to display checkboxes on the product details screen of the Shopify theme "Dawn" and enable the purchase button when all are checked

We are sometimes asked to set a checkbox on the Shopify product screen so that the product cannot be purchased (cannot be added to the cart) if it is not checked. The setting method differs depending on the theme, but here is an example of the setting for the Dawn theme.

Setup Step 1: Add the scheme to "main-product.liquid" and the label to "ja.schema.json"

Step 2: Modify the code in "main-product.liquid"

Setup Step 3: Add the "Checkbox before purchase" block in the product information section of the product template