Add default description for clientMutationId
Add default description for clientMutationId

nevesenin/graphql-ruby,nevesenin/graphql-ruby,xuorig/graphql-ruby,rmosolgo/graphql-ruby,xuorig/graphql-ruby,rmosolgo/graphql-ruby,musicglue/graphql-ruby,rmosolgo/graphql-ruby,nevesenin/graphql-ruby,xuorig/graphql-ruby,nevesenin/graphql-ruby,rmosolgo/graphql-ruby