Draft: feat: update to GeoServer 3

[buehner]

This is a branch for all the changes that are required to have the Dockerfile work with GeoServer 3.

It is WIP and should be merged, once GeoServer3 is officially released.

It is running fine with the current GeoServer3 Snapshot WAR file available. @jodygarnett I successfully tested all features of the docker image project (JNDI, CORS, GDAL, etc) and it is working fine! I could not find any issues.

Just try docker-compose -f docker-compose-demo.yml up --build

[jodygarnett]

@buehner I think some of this is handled here:

• https://github.com/geoserver/docker/blob/master/build/release.sh

Or is this PR changing the defaults, to be merged alongside 3.0 release?

[buehner]

Yes. The main intention is to keep track of the defaults.

For a long time, I did not realize that the release script uses the GEOSERVER_BASE_IMAGE argument. That's why I - at that time - introduced the renovate bot to ensure that we always have an explicit, up-to-date version in the Dockerfile.

This brings me to another thought: As the release script uses a non-explicit "generic" version for the base image, this might lead to unwanted behavior: Docker internally caches tagged images once they were downloaded. Unless explicitly using flags like --pull, Docker would NOT pull new versions, even if they are available on a hub. And those images usually update often in the docker world, so we - at least in theory - miss security updates etc.

So I created this PR to adress this potential issue: #292

[jodygarnett]

So GeoServer 3.0.0 is released, but main-nightly has been failing for a little while.

Now that it is working I observe the following on build server:

Downloading GeoServer for version 3.1-SNAPSHOT
  Download GeoServer 3.1-SNAPSHOT
  Download nightly build from https://build.geoserver.org/geoserver/3.1.x
  downloading geoserver-3.1.x-latest-war.zip
Build step 'Execute shell' marked build as failure

The URL should be https://build.geoserver.org/geoserver/main/geoserver-main-latest-bin.zip

[jodygarnett]

I think this PR has gone stale, as https://github.com/geoserver/docker/blob/master/build/release.sh presently makes a judgement call on which base image to use.