restfull api: Health check 規範

healthcheck方法返回版本、日期，便於普羅米修斯等工具監控apiproject 的狀態、是否存活、版本是否正確

方案一
一個project添加一個api: healthcheck
Java springboot + maven sample:
1.pom.xml add:

   <resources>
      <resource>
        <directory>src/main/resources.${deploy.type}</directory>
        <filtering>true</filtering>
      </resource>
    </resources>

2.application.yml add:

version: @project.version@

3. class add api method:

    @Value("${version}")
    private String version;

    @RequestMapping(value = "/healthcheck", method = RequestMethod.GET)
    public Response<?> healthcheck() {

        return Response.success(version + System.currentTimeMillis());
    }