At the top of the theme show page we have a link
to the theme About and License, which are supposed
to be URLs. However some themes have left placeholder
text in these metadata fields, which leads to a wonky
experience.
Instead, we can just not serialize these fields if they
are not valid URLs, then they will not show as links
in the UI.
The value field of ThemeField is only used when viewing a diff in the staff action logs and local theme editing. value is being serialized into the theme index as well, which is not used. It's a huge amount of JSON that we can cut by removing it.
This also breaks up the various theme serializers into separate classes so they autoload properly (or at least restart the server on edit)