Reserved prefix protection for metafields and metaobjects

Starting today, reserved prefixes have been widened to include any phrase. You can no longer make any metafield namespace or metaobject type that includes -- (e.g., foo-- , foo--bar ). This only affects new metafield and metaobject definitions; existing definitions will continue to work as before. This change is intended to reserve the -- format for platform defined features such as shopify--{standard} and app--{your-app-id}.