Test and document EG_GATEWAY_CONFIG_PATH setting

We no longer build different docker containers for the different ooapi
gateway versions.

To simulate the production use, we put the different
gateway.config.v*.yml files in ./test/config, which is mounted into
the docker image, and the file to be used is set by specifying the
EG_GATEWAY_CONFIG_PATH.

.dockerignore

@@ -0,0 +1,7 @@
+*
+!policies
+!*.json
+!*.js
+!lib
+!vendor
+!config

Dockerfile

@@ -1,8 +1,6 @@
 FROM node:18 AS build-env
 COPY . /app
 WORKDIR /app
-RUN cp config/system.config.yml.prod config/system.config.yml
-RUN rm -rf node_modules
 RUN npm ci --only=production
 
 FROM gcr.io/distroless/nodejs:18

README.org

@@ -457,6 +457,20 @@ brew:
 
   To build the image
 
+** Location of system.config and gateway.config files and docker mounts
+
+The docker container does not contain a gateway configuration file.
+
+By default, the gateway loads ~system.config.yml~ and
+~gateway.config.yml~ from the ~./config~ directory. The ~./config~
+directory contains additional model files that must be present.
+
+To run the gateway in docker with a mutable configuration, it's
+recommended to read-write mount a directory containing the gateway
+configuration files and to set the ~EG_SYSTEM_CONFIG_PATH~ and
+~EG_GATEWAY_CONFIG_PATH~ environment variables to point to the files
+to use in that directory.
+
 * Setting up development environment