ElasticSearch 7.x support

[AurelienConte]

I want to integrate the ElasticSearch source to cube.dev but it seem to be not compatible with the latest version of Elastic (7.X)
There is any plan to support it ?

Thanks,

[github-actions]

If you are interested in working on this issue, please leave a comment below and we will be happy to assign the issue to you.
If this is the first time you are contributing a Pull Request to Cube.js, please check our contribution guidelines.
You can also post any questions while contributing in the #contributors channel in the Cube.js Slack.