Have stage permissions

The issue BAM-9613 was closed when the Deployment plans were introduced, however I do not think it should have been closed, as it did not implement this useful improvement.

Please allow manual stage triggers to have specific permissions tied to them.

Use cases outside of deployment:

• Wanting automated processes to stop at a certain point, and resume only when a specific person/group triggers it to. Ex: Integration tests that could be destructive to other users in the environment. Chaos Monkey / Performance stress tests. Etc.
• As an indicator + control flow leading up to a deployment that the documentation / external notifications are ready.
• As a simple logged + recorded compliance measure that "foo has signed off on this before bar occurred"
• Locking the stage to only be able to be able to progress when a service account triggers the stage via REST API due to an event / check in it's business logic / lifecycle occurred.

And many more. As a process gets further along it tends to be able to be kicked off by many, but require more escalation towards the end. And to capture the whole process requires the need to restrict certain stages to certain groups.