Attribute injection needs to be smarter

[jbusecke]

I am actually pretty happy I got this to work: https://github.com/leap-stc/proto_feedstock/blob/d3d198b496e42a7ca3702e1b34a9c3426220575d/feedstock/recipe.py#L68-L101

But it causes all kinds of trouble in the local execution context (which I am now testing in #23 and linked there). Unless we can make that work in both contexts I think we should not package it in this template. Maybe something that we should publish as a self contained stage in the data-management-utils repo (also pinging @norlandrhagen here whos work might have overlapped with this at some point?)