Check size limits on metadata and name set from client. (#2850)

* Send error response when update metadata fails.

Keeping it simple for the first implementation.
- Send error response only if request_id != 0
- Two kinds of errors notified
  o does not have permissions - NOT_ALLOWED
  o attributes exceeds size limits -  INVALID_ARGUMENT

* Check size limits on metadata and name set from client.

Added a name length limit also.

* check name length in service update participant path also

* limit check in limit config

* update protocol

* longer keys

pkg/service/auth_test.go

@@ -29,7 +29,7 @@ import (
 
 func TestAuthMiddleware(t *testing.T) {
 	api := "APIabcdefg"
-	secret := "somesecretencodedinbase62"
+	secret := "somesecretencodedinbase62extendto32bytes"
 	provider := &authfakes.FakeKeyProvider{}
 	provider.GetSecretReturns(secret)