Disabled products should not show up in a search query result

[mschipperheyn]

Describe the feature
The search query allows you to search for products based on a number of inputs. Product:enabled is not one of them. And yet when you disable a product you want to be sure it disappears from the query results.

Expected behavior
There should be a flag to filter out disabled products, which should default to true

Workaround
Filter the disabled results out at the client level. However, this screws with pagination.

Environment (please complete the following information):

• @vendure/core version: 3.0.4