This middleware looks at the list of types that will be sent to
Elasticsearch, if it's an empty array, it sends an error response before
Elasticsearch is even quieried, because Elasticsearch interprets an
empty type array as "search anything" rather than the intended "don't
search anything".
This moves the list of types created by sanitising the layer API
parameter from clean.layers to clean.types.from_layers. In subsequent
commits, types created from address parsing, and the
yet-to-be-implemented source parameter will also live in the clean.types
object.
This will allow moving logic to set cmd.type out of controllers, and
into separate logic that can be a littler smarter. Also, it will no
longer require the clean.default_layers_set flag to be passed all around
like a nasty global variable.
Refactor search and doc controllers to allow for post-processing middleware
to handle geojson and response sending. Allows for a much more flexible routing scheme.