The file cache was caching the `Unauthorized` errors if a user without
the right perms opened the file first. So all future opens would fail.
Now the cache always opens with a subject that can read files. And authz
is checked on the Acquire per user.
Existing template versions do not have the metadata (modules + plan) in
the db. So revert to using static parameter information from the
original template import.
This data will still be served over the websocket.
