Provide a docker-compose stack for testing

[mcbridematt]

I hope this is useful to somebody.

This adds a docker-compose stack and supporting container files to run a working XConf instance.

The configuration is similar to the steps described on wiki.rdkcentral.com and should not be relied upon for production purposes without modification.

CONTAINER ID  IMAGE                                      COMMAND               CREATED     STATUS      PORTS                    NAMES
bf2d170e8002  docker.io/library/cassandra:4.1.8          cassandra -f          6 days ago  Created                              xconfserver_cassandra_1
3d518b33afd9  localhost/xconfserver_initdb:latest                              6 days ago  Created                              xconfserver_initdb_1
233d7a02abd3  localhost/xconfserver_xconfangular:latest  java -jar /usr/lo...  6 days ago  Created     0.0.0.0:19093->8080/tcp  xconfserver_xconfangular_1
0201c9dd85a8  localhost/xconfserver_xconfdata:latest     java -jar /usr/lo...  6 days ago  Created     0.0.0.0:19092->8080/tcp  xconfserver_xconfdata_1

Tested hosts:

• docker-compose 1.29.2 / docker 24 on Linux/x86_64
• podman-compose 1.4.0 / podman 4.9.3 on Linux/arm64

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