Makefile update to support Docker based target

Added new "code-gen-docker" target.

Change-Id: I0184b309000ee0ccac5885f758688a3053f6fb91

Makefile

@@ -6,6 +6,22 @@ code-gen:
 	go run api_generator.go | gofmt > api/service_interface.go
 	go generate api/service_interface.go
 
+.PHONY: code-gen-docker
+code-gen-docker:
+	rm -rf client
+	docker run --rm -v ${PWD}:/local openapitools/openapi-generator-cli:v4.2.2 generate \
+         -i  /local/spec/openapi.yaml \
+         -g go \
+	 --package-name "client" \
+         --git-repo-id go-redfish/client \
+         --git-user-id airship \
+         --git-host opendev.org \
+	 -p enumClassPrefix=true \
+         -o /local/client
+	mkdir -p api
+	go run api_generator.go | gofmt > api/service_interface.go
+	go generate api/service_interface.go
+
 
 .PHONY: deps
 deps: