feature request: support additional types for compile-time parameters

[redterror]

Hi, currently I am using sparkleformation heavily with a custom CLI to support a particular workflow with Azure. I'm making heavy use of compile-time parameters and generally things are great. One restriction I am bumping into is the limited type support for compile-time parms, e.g. just number or strings. I'd like to have arrays and hashes available. Here's an example that I hope illustrates my use case:

YAML params:

---
data_disk0_size: 128
data_disk0_lun: 0

various_other_params: ...

Compile-param definition:

module MyStuff
  module Params
    DATA_DISK = {}
    (0..4).each do |idx|
      DATA_DISK["data_disk#{idx}_lun".to_sym]           = { type: :number, description: "LUN to use for this disk.", default: nil }
      DATA_DISK["data_disk#{idx}_size".to_sym]          = { type: :string, description: "Disk size in GB.", default: nil }
      DATA_DISK["data_disk#{idx}_caching_type".to_sym]  = { type: :string, description: "Cache type for this disk", allowed_values: %w(None ReadOnly ReadWrite), default: "None" }
      DATA_DISK["data_disk#{idx}_create_option".to_sym] = { type: :string, description: "How to create this disk", allowed_values: %w(fromImage empty attach), default: "empty" }
      DATA_DISK["data_disk#{idx}_account_type".to_sym]  = { type: :string, description: "Storage account type for this disk.", allowed_values: %w(Standard_LRS Premium_LRS), default: "Standard_LRS" }
    end
    DATA_DISK.freeze
  end
end

Template:

SparkleFormation.new(:generic_host, :provider => :azure, :compile_time_parameters => ::MyStuff::Params::DATA_DISK.merge(... other params)).load(:base) do
  data_disks = (0..4).collect {|idx|
    disk_cfg = %w(lun size caching_type create_option account_type).collect{ |key|
      [key.to_sym, state!("data_disk#{idx}_#{key}".to_sym)]
    }.to_h
    # Get rid of empty disks in this array
    if disk_cfg[:size].nil?
      nil
    else
      disk_cfg
    end
  }.compact

  dynamic!(:my_node, :node1, {data_disks: data_disks, ... other params})
end

What I would like to do is something more like:

Yaml:

---
data_disks:
  -
    size: 128
    lun: 0
other_params: ...

Compile param definition:

module MyStuff
  module Params
    DATA_DISK = { 
      type: :array, 
      allowed_values: { 
        size: { default: nil, type: :number }, 
        caching_type: { type: :string, allowed_values: %w(None ReadOnly ReadWrite), default: "None" }
      }
   }
    DATA_DISK.freeze
  end
end

I'm not sure the best way to capture the DATA_DISK definition in this context, but perhaps inspiration can be drawn from strong_params? That might be overkill, anyway, just a thought.