OpenAPI Documentation: improve type parsing

[splitbrain]

Type parsing currently does not support multiple types like int|bool nor does it support a way to define a typed associative array. Eg. an API that returns a structue of array("key1" => Page, "otherkey" => Page) where Page is one of our APIResponse objects can not be defined as a typehint currently.

It should be explored how to add these features to the doc block parsers and integrate the resulting structures into the generated OpenAPI spec.