add user agent internal metadata (#4967)

CHANGELOG_PENDING.md

@@ -1,4 +1,6 @@
 ### SDK Features
+* `aws/corehandlers`: Add internal flag in user agent functionality
+  * Added handler which will add aws internal metadata to the user agent string
 
 ### SDK Enhancements
 

aws/corehandlers/awsinternal.go

@@ -0,0 +1,4 @@
+// DO NOT EDIT
+package corehandlers
+
+const isAwsInternal = ""

aws/corehandlers/user_agent.go

@@ -35,3 +35,13 @@ var AddHostExecEnvUserAgentHander = request.NamedHandler{
 		request.AddToUserAgent(r, execEnvUAKey+"/"+v)
 	},
 }
+
+var AddAwsInternal = request.NamedHandler{
+	Name: "core.AddAwsInternal",
+	Fn: func(r *request.Request) {
+		if len(isAwsInternal) == 0 {
+			return
+		}
+		request.AddToUserAgent(r, isAwsInternal)
+	},
+}

aws/defaults/defaults.go

@@ -74,6 +74,7 @@ func Handlers() request.Handlers {
 	handlers.Validate.PushBackNamed(corehandlers.ValidateEndpointHandler)
 	handlers.Validate.AfterEachFn = request.HandlerListStopOnError
 	handlers.Build.PushBackNamed(corehandlers.SDKVersionUserAgentHandler)
+	handlers.Build.PushBackNamed(corehandlers.AddAwsInternal)
 	handlers.Build.PushBackNamed(corehandlers.AddHostExecEnvUserAgentHander)
 	handlers.Build.AfterEachFn = request.HandlerListStopOnError
 	handlers.Sign.PushBackNamed(corehandlers.BuildContentLengthHandler)