Allow attribute substitution in attributes defined in playbook and component descriptor
There's attribute substitution in attributes defined in a document:
:a: 1
:b: {a}
b is {b} //1
Extend this to attributes defined in the playbook and component descriptor, using the same {} syntax for the computed value.
The order of the list of candidate values needs to be defined. I believe it would be
playbook
component descriptor
document
Command line values need to be included in the list also. Where? Should attributes set on the command line also allow substitution?