support using master key subaccount header

lib/sparkpost_rails.rb

@@ -25,6 +25,8 @@ class Configuration
     attr_accessor :transactional
     attr_accessor :ip_pool
 
+    attr_accessor :subaccount
+
     def initialize
       set_defaults
     end
@@ -46,6 +48,8 @@ def set_defaults
 
       @transactional = false
       @ip_pool = nil
+
+      @subaccount = nil
     end
   end
 end

lib/sparkpost_rails/delivery_method.rb

@@ -336,6 +336,16 @@ def prepare_api_headers_from sparkpost_data
         "Authorization" => api_key,
         "Content-Type"  => "application/json"
       }
+
+      if sparkpost_data.has_key?(:subaccount)
+        subaccount = sparkpost_data[:subaccount]
+      else
+        subaccount = SparkPostRails.configuration.subaccount
+      end
+
+      if subaccount
+        @headers["X-MSYS-SUBACCOUNT"] = subaccount.to_s
+      end
     end
 
     def post_to_api

spec/subaccount_api_spec.rb

@@ -8,7 +8,7 @@
   end
 
   context "Subaccount API Key" do
-    it "handles uses supplied subaccount key instead of default API key" do
+    it "uses supplied subaccount key instead of default API key" do
       SparkPostRails.configure do |c|
         c.api_key = 'NEW_DEFAULT_API_KEY'
       end
@@ -30,4 +30,46 @@
       expect(@delivery_method.headers).to include("Authorization" => "NEW_DEFAULT_API_KEY")
     end
   end
+
+  context "Subaccount ID" do
+    it "accepts a subaccount ID in the configuration" do
+      SparkPostRails.configure do |c|
+        c.subaccount = 123
+      end
+
+      test_email = Mailer.test_email
+      @delivery_method.deliver!(test_email)
+
+      expect(@delivery_method.headers).to include("X-MSYS-SUBACCOUNT" => "123")
+    end
+
+    it "defaults to no subaccount ID in the configuration" do
+      expect(SparkPostRails.configuration.subaccount).to eq(nil)
+    end
+
+    it "accepts subaccount ID for an individual message" do
+      test_email = Mailer.test_email sparkpost_data: {subaccount: 456}
+      @delivery_method.deliver!(test_email)
+
+      expect(@delivery_method.headers).to include("X-MSYS-SUBACCOUNT" => "456")
+    end
+
+    it "uses subaccount ID on message instead of value in configuration" do
+      SparkPostRails.configure do |c|
+        c.subaccount = 123
+      end
+
+      test_email = Mailer.test_email sparkpost_data: {subaccount: 456}
+      @delivery_method.deliver!(test_email)
+
+      expect(@delivery_method.headers).to include("X-MSYS-SUBACCOUNT" => "456")
+    end
+
+    it "does not include the subaccount header when none is specified" do
+      test_email = Mailer.test_email
+      @delivery_method.deliver!(test_email)
+
+      expect(@delivery_method.headers.has_key?("X-MSYS-SUBACCOUNT")).to eq(false)
+    end
+  end
 end