[rackspace|compute] Add attachments model and collection.

Provide a method for attaching, listing, and detaching block
storage volumes on Rackspace next-generation cloud servers.

lib/fog/rackspace/compute_v2.rb

@@ -24,6 +24,8 @@ class BadRequest < Fog::Rackspace::Errors::BadRequest; end
       collection :flavors
       model :image
       collection :images
+      model :attachments
+      collection :attachments
 
       request_path 'fog/rackspace/requests/compute_v2'
       request :list_servers
@@ -44,6 +46,11 @@ class BadRequest < Fog::Rackspace::Errors::BadRequest; end
       request :list_flavors
       request :get_flavor
 
+      request :attach_volume
+      request :get_attachment
+      request :list_attachments
+      request :delete_attachment
+
       class Mock
         def request(params)
           Fog::Mock.not_implemented

lib/fog/rackspace/models/compute_v2/attachment.rb

@@ -0,0 +1,34 @@
+require 'fog/core/model'
+
+module Fog
+  module Compute
+    class RackspaceV2
+      class Attachment < Fog::Model
+        identity :id
+
+        attribute :server_id, :aliases => 'serverId'
+        attribute :volume_id, :aliases => 'volumeId'
+        attribute :device
+
+        def save
+          requires :server, :identity, :device
+          data = connection.attach_volume(server.identity, identity, device)
+          merge_attributes(data.body['volumeAttachment'])
+          true
+        end
+
+        def destroy
+          requires :server, :identity
+          connection.delete_attachment(server.identity, identity)
+          true
+        end
+
+        private
+
+        def server
+          collection.server
+        end
+      end
+    end
+  end
+end

lib/fog/rackspace/models/compute_v2/attachments.rb

@@ -0,0 +1,25 @@
+require 'fog/core/collection'
+require 'fog/rackspace/models/compute_v2/attachment'
+
+module Fog
+  module Compute
+    class RackspaceV2
+      class Attachments < Fog::Collection
+
+        model Fog::Compute::RackspaceV2::Attachment
+
+        attr_accessor :server
+
+        def all
+          data = connection.list_attachments(server.id).body['volumeAttachments']
+          load(data)
+        end
+
+        def get(volume_id)
+          data = connection.get_attachment(server.id, volume_id).body['volumeAttachment']
+          data && new(data)
+        end
+      end
+    end
+  end
+end

lib/fog/rackspace/requests/compute_v2/attach_volume.rb

@@ -0,0 +1,23 @@
+module Fog
+  module Compute
+    class RackspaceV2
+      class Real
+        def attach_volume(server_id, volume_id, device)
+          data = {
+            'volumeAttachment' => {
+              'volumeId' => volume_id,
+              'device' => device
+            }
+          }
+
+          request(
+            :body => Fog::JSON.encode(data),
+            :expects => [200],
+            :method => 'POST',
+            :path => "servers/#{server_id}/os-volume_attachments"
+          )
+        end
+      end
+    end
+  end
+end

lib/fog/rackspace/requests/compute_v2/delete_attachment.rb

@@ -0,0 +1,15 @@
+module Fog
+  module Compute
+    class RackspaceV2
+      class Real
+        def delete_attachment(server_id, volume_id)
+          request(
+            :expects => [202],
+            :method => 'DELETE',
+            :path => "servers/#{server_id}/os-volume_attachments/#{volume_id}"
+          )
+        end
+      end
+    end
+  end
+end

lib/fog/rackspace/requests/compute_v2/get_attachment.rb

@@ -0,0 +1,15 @@
+module Fog
+  module Compute
+    class RackspaceV2
+      class Real
+        def get_attachment(server_id, volume_id)
+          request(
+            :expects => [200, 203, 300],
+            :method => 'GET',
+            :path => "servers/#{server_id}/os-volume_attachments/#{volume_id}"
+          )
+        end
+      end
+    end
+  end
+end

lib/fog/rackspace/requests/compute_v2/list_attachments.rb

@@ -0,0 +1,15 @@
+module Fog
+  module Compute
+    class RackspaceV2
+      class Real
+        def list_attachments(server_id)
+          request(
+            :expects => [200, 203, 300],
+            :method => 'GET',
+            :path => "servers/#{server_id}/os-volume_attachments"
+          )
+        end
+      end
+    end
+  end
+end