Dependency management

[ColonelPanics]

Smart understanding of soft-linking be sure to protect things that have dependent resources. For example, don't delete a domain if there are deployed resources that have used it as a parameter.

Probably worth holding off until #221 has been implemented.

[WilliamMcCumstie]

So there are two options here on how to handle dependencies. In this issue I will discussed an initial implementation and then I'll open an issue on advanced graph theory.

Now that Models::Deployment is getting retired and replaced with Models::Domain and Models::Node it makes the dependency management quasi easier. For the most part, Nodes are dependant on the Domain.

Therefore, there needs to be a new Models::Node#dependencies instance method. This method should return one of the following options:

1. A single element array: [<#Models::Domain...>] if the node depends on the domain
2. A empty array: [] if the node does not depend on the array

By doing this, we will cover the vast majorities of use cases where a node depends on its domain. It might be worth adding a dependencies instance method onto Models::Domain, but it should only return an empty array for the time being

EDIT: Scratch this plan - see below

[WilliamMcCumstie]

Once the simplified dependencies management has been implemented, then all the dependencies need to be created before the Node is created

[WilliamMcCumstie]

From discussions IRL, a trimmed down version will be used. Deploying a node will no longer implicitly trigger the domain (or another node) to be deployed.

Instead the dependencies list should be checked to insure all the required nodes (+domain) are running. If they are not, then an error should be raised