Refactor rule category field to extract paths calculation to API

It was calculated with the category paths and search tokens in the RuleFeed.  Moved this logic to the API.

Now it only receives a list of category ids and the category paths as well as the search tokens are calculated in the API
this is the line that causes the binding exception. now it's within a flatMap in a future response, so I found like a good solution so support that exception in the withErrorHandling method