Advertise the version tag in presets API

To test locally, you will need to define the version as an env variable:

cat <<EOF > .env
PRESETS_ENABLE_SSL=TRUE
PRESETS_BACKEND_PORT=4443
PRESETS_BACKEND_PORT_HTTP=80
EXTERNALADDRESS=https://localhost:4443/
OAUTH2_USERINFO=https://gitlab.com/oauth/userinfo
VERSION=somethingsomething
EOF

docker-compose up -d --build

You should be able to see the API call in action by using the /version endpoint through Docker:

belen@belen-knmi:~/devel/presets-backend/Docker$ curl -kL https://0.0.0.0:4443/version
{"version":"somethingsomething"}

To test in an actual branch: https://gwpresetsbe-dev-implementversionapi.geoweb.dev.knmi.cloud/version

You should be able to see something like:

// 20220726103952
// https://gwpresetsbe-dev-implementversionapi.geoweb.dev.knmi.cloud/version

{
  "version": "versionapi"
}

Ticket opengeoweb/opengeoweb#2312 (closed) cannot be closed until this one and the deploy-preset-backend MR have both been approved and merged.