build: Improved the Dockerfile to make the project less hostile to use with docker

[GCastilho]

Problem: Some behaviors of the project are hostile to use in a docker environment, that includes:

• The user being node instead of the default root, which limits mountpoints with write access
• The configuration files not being in a single folder, requiring individual mounts for each file
• The config files needing to the mapped using environment variables to a location where the node user has write permissions to allow the use with volumes - this happens because the default behavior when the target does not exists for volume creation is to create a folder, which breaks the script since it expects the .json to be a file
• The database can't be mapped to a different folder - this one is the motivation for the PR: for the reasons described in the previous point, we can't create a mountpoint for the db.json, in which case it will stay in the container filesystem and lost upon restart, which is unacceptable

Solution: Refactor the Dockerfile to change default locations for the .json files and add support for a different location for the db.json

I've refactored the Dockerfile to set ENVs changing the default location for all the config files (read using readConfigPathsFromENV) to be in the /root folder (root's home), this allow easy mapping of the /root folder to a volume

The user for the docker process was also removed, it's now the default root user - A different user for the docker process is only useful in very specific cases, in general, it's not a problem to run the process as root since the container is already an isolated environment; and, since it was causing permission problems for the volume mountpoints, I've removed it

I've also refactored the Dockerfile to use two stages, one for build and other for the live image, that should reduce the image size and reduce the code shipped in the image. The behavior is the same

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The only change in program code was the addition of the CONFIG_DB_PATH to allow specifying a different path for the db and the db initialization to use that config instead of the hardcoded 'db.json'. All the other changes were in the Dockerfile and should only affect docker images

[Joohansson]

Sounds good. I'm curious about the mapping of json files. Is this change breaking in any way, such that people running the container will have to move their config files?

[GCastilho]

By default the files will be mapped to the volume in /root, but these locations can be overwritten passing an environment variable to the container

[Joohansson]

@GCastilho This is how my docker composer config looks today. So with this change, I would only have to make one mapping if I got it right. That is from the folder where I keep the config files to /root?

Something like this?
./:/root

[GCastilho]

@Joohansson Correct, your volumes: may look something like this:

 - ./myLocalConfigFolder:/root

and that will map all your JSON files to 'myLocalConfigFolder'

[aspic]

Awesome improvement!