support time-based windows on warehouses and stages

[krancour]

For Warehouses, allow specifying time periods where new Freight can/cannot be produced.

For Stages, allow specifying time periods where Promotions may/may not occur.

Edit: It might be better to include these features in ProjectSpec.

[lknite]

This came in as a requirement for us, or something similar, we need to be able to do a "freeze" such as a winter holiday freeze, or "no changes around earnings" freeze, or similar. The ability to perform some sort of check like a Job before a promotion is allowed would work as well.

[lknite]

I received clarification on the use cases:

• "I'm thinking more of a scenario where we have an incident happening in production and we want to halt all changes into that environment. This would be more of an emergency button to stop all deployments."

• "We need this when we do patching, DR exercises, or when there's an incident"

If there was the ability to run a Job before a promotion, that would work also cause I could have it check for an on/off switch that we could turn off. I could make sure its added to all stages. Of course, something at more of a top-level would be much simpler.

[krancour]

@lknite there was a separate issue for a "stop the line button." It might have gone stale and been closed. I'll find it and re-open that.

[krancour]

@lknite I re-opened #1422

[gmauleon]

That would work well for "maintenance windows" where depending on the cluster you deploy on, you have specific time frames when promotion are allowed.