Property Registries should allow IntoSchema instances #1181
Description
Currently, adding an IntoSchema instance, e.g. (m/enum-schema) to property registry fails, bucause it expects to have all schemas serializable. This constraint doesn't make sense as you can already add non-serializable object into properties, for example :gen/gen expects to have a test-check generator instance.
We should allow any valid registry as property registry. See #780, #1048.