[Bug] dynamic_cred helper not exposed through calm.dsl.runbooks

[nutken]

Describe the bug Attempting to create endpoint with dynamic credentials. With static credentials, the basic_cred helper is imported from calm.dsl.runbooks. The expectation is dynamic_cred helper be available as well, however it is not.

Branch/Container master

Workaround dynamic_cred helper can be imported from calm.dsl.builtins.models.credential