Adds a new yaql function 'decryptData' which pairs with 'encryptData' on
the dashboard side.
Requires a valid secret storage backend (e.g. Barbican) to be configured
via Castellan in murano.conf, e.g.
[key_manager]
auth_type = keystone_password
auth_url = <auth_url>
username = <username>
password = <password>
project_id = <project_id>
user_domain_name = <user_domain_name>
Murano will still work fine without this config but the encrypt/decrypt
functions will be unavailable.
Partially-Implements blueprint: allow-encrypting-of-muranopl-properties
Depends-On: I1be3a1e11e3f4c2170062927ad359bf679eb25d9
Change-Id: I09416b6d35ed2dafa823eca98262a4e23081e6eb