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This will ease up the migrations, as those are the only tables we
absolutely need to keep the content of. It will be easier to just create
a new version of the model, and include it from the migration script,
instead of having the main "create table" and the migration one

This matches the unix fs actual implementation

For consistency

We now return all media as a single query

Mostly for consistency with the other methods

Partial listing (ie. not calling all() ) was failing for requests with
no parameters.