Dockerfile improvement

[zhming0]

• Improves docker image security: use non root user, as numeric user id.
• Use fully qualified image url in from clause (so podman can build it too).
• Use builder pattern so dockerfile is self contained now.
• a .dockerignore file.

Thank you for making this software 🙂 . I am enjoying using it.

[anderspitman]

Hi @zhming0. Thanks for the contribution! I probably won't merge this because I prefer the alpine images. They're much smaller in my experience. If you want to make similar improvements to the alpine image, they would be welcome, but don't feel any obligation to do so. I'm happy to keep this open so others can find your dockerfile. I'm sure some would find it useful.

[zhming0]

@anderspitman no problem at all. I changed it to Alpine now, please review 🙏🏿 . I love small image too 🙂.

FYI, in this case it's a 24MB vs 60MB difference.

[anderspitman]

Thanks @zhming0! I'll take a look soon. Since this Dockerfile is used for the production deployment I need to test and make sure it works.

[anderspitman]

Turns out I was wrong. I'm not currently using this Dockerfile for production. I did a quick review and just have a couple requests.

[anderspitman]

Sorry for the delay! Thanks again @zhming0