Add lifecycle policy for nauth resources

[kejne]

Is your feature request related to a problem? Please describe.
Accounts are critical resources where an unintended deletion could cause a lot of problems with potentially causing cascading effects.

Describe the solution you'd like
Tools such as Crossplane use lifecycle policies to manage how resources are managed. For example, the account could take control of an existing account or be set to only add & update.

Describe alternatives you've considered
To configure NATS to not allow deletions, which could be an option as well.

[kejne]

Limited lifecycle functionality has been added with #82.
This adds functionality using labels for now. Moving this to the CRD would be useful long term.