POST for /api/v1/products/:product_id/idea_categories

We want the Categories that an Idea is assigned to, to be 1:1 with our Components from Jira. We could utilize the JIRA Rest API and the AHA Rest API to keep these two lists in sync, however the AHA API only has a GET protocol available and lacks a POST protocol that we could utilize to maintain the two libraries.

This functionality will greatly assist us as we look to leverage AHA Ideas across our Client platforms for all our product lines.