Feature request: Approve only strategy

[mpanichella]

could you add a new strategy that is just approval? This would be very useful because when you have microservices and releases are generated, not always to deploy all the microservices, but only those that are pending approval because they had any changes On the other hand, the Release Definition, it would be good to be able to select more than one, for example with a field separated by commas, for the same reason, that I mentioned above