Currently pages get their <head><meta> data copied verbatim from templates, implemented in GUISE-33. We need instead to dynamically generate these <meta> tags from the contents of the actual metadata from e.g. GUISE-36.
This will allow adding extra metadata that users have added e.g. in sidecar files (as part of a future ticket).
Some RDFa metadata such as Open Graph og:title will need a prefix attribute generated.
We'll need to remove mummy: metadata (see ).