Add config and documentation for running dirsrv with Docker

README.md

@@ -31,10 +31,24 @@ Running all specs:
 
     bundle exec rspec
 
+### Docker (Compose)
+
+There is a working Dockr Compose config file, which allows you to spin up both
+an app server for Rails as well as a local 389ds (LDAP) server.
+
+By default, `docker-compose up` will only start the LDAP server, listening on
+port 389 on your machine. Uncomment other services in `docker-compose.yml`.
+
 ### LDAP server
 
-TODO make it easy to run a local Kosmos LDAP server for development, without
-manual LDIF imports etc. (or provide a staging instance)
+See the previous section for quickly spinning up an LDAP server with Docker (or
+edit your environment configuration to use an existing one).
+
+After creating the Docker container for the first time (or after deleting it),
+you need to run the following command once, in order to create the dirsrv
+back-end:
+
+    docker-compose exec ldap dsconf localhost backend create --suffix="dc=kosmos,dc=org" --be-name="dev"
 
 ## Documentation