docker: dockers images, first draft:

This patch introduce new docker images, replacing the unmaintained ones which were in
sat_docs.

Images + docker-compose files are provided to use SàT backend and Libervia, but also to
integrate and configure Prosody and SàT PubSub to run end-to-end tests.

docker/docker-compose_e2e.yml

@@ -0,0 +1,42 @@
+version: "3.6"
+services:
+
+  prosody:
+    build: prosody_e2e
+    image: salutatoi/prosody_e2e
+    depends_on:
+      # we need to depend on sat to get IP address of the container for conf
+      - sat
+    tmpfs: /var/lib/prosody
+    tmpfs: /var/log/prosody
+    networks:
+      default:
+        aliases:
+          - server1.test
+          - server2.test
+          - server3.test
+
+  db:
+    image: postgres
+    environment:
+      POSTGRES_PASSWORD: test_e2e
+      POSTGRES_DB: pubsub
+    tmpfs: /var/lib/postgresql/data
+
+  pubsub:
+    build: pubsub
+    image: salutatoi/sat_pubsub
+    depends_on:
+      - db
+      - prosody
+    environment:
+      PGHOST: db
+      PGUSER: postgres
+      PGPASSWORD: test_e2e
+      SAT_PUBSUB_RHOST: server1.test
+      SAT_PUBSUB_JID: pubsub.server1.test
+      SAT_PUBSUB_XMPP_PWD: test_e2e
+
+  sat:
+    build: backend_e2e
+    image: salutatoi/sat_e2e