Ref and GetAtt Specificiations

[kddejong]

I've been writing some individual checks that would check the Ref or GeAtt of resource properties.

For example we would check the that a Ref for VpcId goes to a resource of AWS::EC2::VPC. If it was to a parameter we would check the parameter is of appropriate type (String, AWS::EC2::VPC::Id)

Type: "AWS::EC2::Subnet"
Properties:
  CidrBlock: String
  VpcId: String

After writing a few of these I'm starting to see a lot of repeat and I'm wondering if this would be better defined in a JSON/YAML document. We can then write a singular rule to check these items limiting repeated code.
An example of that document is as follows.

{
  "RelationshipTypes": {
    "String": {
      "Ref": {
        "Parameters": [
          "String"
        ]
      }
    },
    "VpcId": {
      "Ref": {
        "Resources": [
          "AWS::EC2::VPC"
        ],
        "Parameters": [
          "String",
          "AWS::EC2::VPC::Id"
        ]
      },
      "GetAtt": {
        "AWS::EC2::SecurityGroup": "VpcId"
      }
    }
  },
  "ResourceTypes": {
    "AWS::EC2::Subnet": {
      "Properties": {
        "VpcId": {
          "RelationshipType": "VpcId"
        },
        "MapPublicIpOnLaunch": {
          "RelationshipType": "String"
        }
      }
    }
  }
}

[kddejong]

This model is built out. Going to call this done for now.