adding support for built-in AWS policies

src/main/scala/com/monsanto/arch/cloudformation/model/resource/IAM.scala

@@ -81,10 +81,30 @@ object `AWS::IAM::ManagedPolicy` extends DefaultJsonProtocol {
   implicit val format: JsonFormat[`AWS::IAM::ManagedPolicy`] = jsonFormat8(`AWS::IAM::ManagedPolicy`.apply)
 }
 
+
+case class AWSManagedPolicy(name: String) {
+  def buildARN = s"arn:aws:iam::aws:policy/$name"
+}
+
+case class ManagedPolicyARN private(resource: Either[ResourceRef[`AWS::IAM::ManagedPolicy`], AWSManagedPolicy])
+object ManagedPolicyARN extends DefaultJsonProtocol {
+  implicit val format: JsonFormat[ManagedPolicyARN] = new JsonFormat[ManagedPolicyARN]{
+    def write(obj: ManagedPolicyARN) =
+      obj.resource match {
+        case Left(ref) => ref.toJson
+        case Right(arn) => JsString(arn.buildARN)
+      }
+    def read(json: JsValue) = ???
+  }
+
+  implicit def fromAWSManagedPolicy(p: AWSManagedPolicy): ManagedPolicyARN = ManagedPolicyARN(Right(p))
+  implicit def fromManagedPolicy(p: ResourceRef[`AWS::IAM::ManagedPolicy`]): ManagedPolicyARN = ManagedPolicyARN(Left(p))
+}
+
 case class `AWS::IAM::Role`(
   name:                     String,
   AssumeRolePolicyDocument: PolicyDocument,
-  ManagedPolicyArns:        Option[Seq[ResourceRef[`AWS::IAM::ManagedPolicy`]]] = None,
+  ManagedPolicyArns:        Option[Seq[ManagedPolicyARN]] = None,
   Path:                     Option[Token[String]] = None,
   Policies:                 Option[Seq[Policy]] = None,
   override val Condition: Option[ConditionRef] = None

src/test/scala/com/monsanto/arch/cloudformation/model/resource/IAMRole_UT.scala

@@ -0,0 +1,41 @@
+package com.monsanto.arch.cloudformation.model.resource
+
+import com.monsanto.arch.cloudformation.model.ResourceRef
+import org.scalatest.{FunSpec, Matchers}
+import spray.json.{JsObject, JsString, _}
+
+
+class IAMRole_UT extends FunSpec with Matchers {
+  describe("AWS::IAM::Role") {
+
+    it("should handle both AWS Managed and Customer policies into valid json") {
+      val customerPolicy = `AWS::IAM::ManagedPolicy`("customer-policy", PolicyDocument(Seq()))
+      val awsPolicy = AWSManagedPolicy("AdministratorAccess")
+
+      val fakePolicyDoc = PolicyDocument(Seq(
+        PolicyStatement(
+          "Allow",
+          Some(DefinedPrincipal(Map("Service" -> Seq("config.amazonaws.com")))),
+          Seq("sts:AssumeRole")
+        )
+      ))
+
+      val expectedJson = JsObject(
+        "name" -> JsString("role"),
+        "AssumeRolePolicyDocument" -> fakePolicyDoc.toJson,
+        "ManagedPolicyArns" -> JsArray(
+          JsObject("Ref" -> JsString("customer-policy")),
+          JsString("arn:aws:iam::aws:policy/AdministratorAccess")
+        )
+      )
+
+      val role = `AWS::IAM::Role`(
+        "role",
+        fakePolicyDoc,
+        ManagedPolicyArns = Some(Seq(ResourceRef(customerPolicy), awsPolicy))
+      )
+
+      role.toJson should be(expectedJson)
+    }
+  }
+}