Agree on API for agent inventory queries

I want to start logging these here to loop in @ivanminutillo as I work through porting Shroom to work on the latest vf-graphql spec. So far it has been minor things like allowing string IDs (in addition to integers) but it will quickly become a discussion about which queries are optimal and easiest to build UIs on top of.

I began with the inventory section of the app. Shroom has Agent.ownedEconomicResources(category: INVENTORY). Here the closest we have is inventoriedEconomicResources().

So the first question is, how to split this up? Separate methods for "owned", "inventoried", "onhand"; or a single query edge for Agent.economicResources that includes a category filter as one of its criteria?