[BUG] Documentation checker tool misses variables containing `{NAME}`

Kind of proposals

• Other

Describe the problem

The documentation checking tool (cmd/documentation-checker/ / make check) is setup to ignore all variables in the Fastly documentation pages that contain {NAME}. This is to ignore the header variables (req.http.*, etc). Which are defined in our predefined.yml file in a different format than the upstream documentation (req.http.%any% vs req.http.{NAME}).

This prevented the tool from noticing variables such as backend.{NAME}.healthy.

Possible solution

This could be fixed by making header regex check more specific to match only the header variables or by removing the regex and instead converting the upstream format to match ours.