Store Customization > Add an identifier to header and footer patterns

[nefeline]

As part of the Pattern Assembler project, the Guidorah team needs to enable a feature to select patterns already inserted in the editor and replace them with other patterns whenever users browse through all options on the sidebar.

But there's a limitation: the moment a pattern is inserted in the editor, there’s no relationship with the source anymore. As a consequence, we have to parse the post content, identify which part corresponds to the inserted pattern, and replace it (at least for now, with WordPress/gutenberg#48458; the strategy here may change).

To facilitate this task, we have to add common identifiers to all header and footer patterns.

Slack convo ref. p1691400488720879-slack-C053716F2H2