self-serve-unresolved-composite-data should reconstruct unresolved param with constant prefix or suffix. 

e.g.

{
"capability-name": "unresolved-composite-data",
"key-mapping": [{
    "output-key-mapping": [{
        "resource-name": "key_name",
        "resource-value": "${vnf_name}_key"
    },
        ...

if vnf_name = abc, resource-value should be resolved to abc_key.