[Feature] 建议k8s部署的时候默认数据库是MySQL，降低使用门槛

[lookhua]

建议k8s部署的时候默认数据库是MySQL，降低使用门槛。
目前随着Tidb等NewSQL数据库的流行，NewSQL会成为技术中台的首选数据库，而Tidb作为一个非常火的项目是搭建技术中台的首选数据库，Tidb兼容MySQL协议而非pg协议，所以incubator-dolphinscheduler的数据直接建在Tidb上是非常合适的

[liwenhe1993]

Good idea!
But why not provide both Mysql and PostgreSql?
When user run DolphinScheduler, they can either choice MySql or PostgreSql.

[chengshiwen]

@lookhua @liwenhe1993 Because of the commercial license, we cannot directly use the driver and client of MySQL. If you want to use MySQL, you can build a new image based on our apache/dolphinscheduler image.

As for MySQL, you need to download mysql-connector-java-5.1.49.jar

1. Create your Dockerfile

FROM apache/dolphinscheduler:latest
COPY mysql-connector-java-5.1.49.jar /opt/dolphinscheduler/lib
RUN apk add --update --no-cache mysql-client

2. Build the image

docker build -f Dockerfile -t apache/dolphinscheduler:mysql .

by the way , please update/add title and description in English