RFE: Allow passing of a custom attribute to a policy condition script

When using Policy Condition Scripts (https://backstage.forgerock.com/#!/docs/openam/13/dev-guide#sec-scripted-policy-condition) it would be useful to be able to pass in a user defined parameter which can be accessed from within the script.

For example, when selecting your script in the policy's 'Environments' tab, there could be an additional field which allows, "foo:bar".
Then in your script you can access this with something like customAttributes.get("foo");