[ENHANCE] Ability to pause rollout of deployments

[tom1299]

Is your feature request related to a problem? Please describe.
We have deployments which have several configmaps and secrets which are often updated almost at the same time. This leads to a series of rollouts for each of the update which (because of lengthy init containers) take a long time to complete.

Describe the solution you'd like
I would like to add the ability to pause the rollout of a deployment for a specific period of time using an annotation. For example:

deployment.reloader.stakater.com/pause-interval: 30s

The behviour of that annotation could be described like this:

• Update of configmap or secret for a deployment is processed
• If the deployment contains the annotation, pause the deployment
• Apply the changes to the deployment as usual (not triggering a rollout because of the pause)
• Add a trigger to resume the deployment after the specified pause interval
• If a change of a configmap or secret for the same deployment occurs during the pause interval, apply the changes (not triggering a rollout because of the pause)
• When the trigger fires, resume the deployment resulting in a rollout with all the updates that occurred during the pause interval

That way updates during the pause interval would result into only one rollout containing all the changes.

Additional context
I opened a pull request #838 with a working draft of the code.
Note that the code is more or less just hacked together in order get something working. If the feature is accepted I would refactor to a better quality.

Thanks in advance for any feedback on this.