Enable Custom Fields on Capacity Planning API Import

We use custom fields to capture KPIs and other key strategic data when creating and maintaining capacity forecasts. There are no facilities - CSV or API - to import these data points which is causing significant work for our product teams. This is exacerbated by the fact that in previous years we used a custom table which meant CSV imports were very straight forward. This product gap - the inability to load any capacity planning data automatically - is impacting the positive reaction to this new functionality and causing manual efforts.

We have a working API process to load Capacity_Investment and Capacity_Estimates data so are ready to leverage the loading of custom fields. Our annual planning cycle has started, hence the request for a fast fix.