Update the README with instructions on initialising the mongo replica set.

README.md

@@ -15,6 +15,56 @@ List of available parameters:
 
 - `GATSBY_API_URL`: override api url (defaults to location origin)
 
+### MongoDB Setup
+
+Mongo needs a couple of extra steps in order to start a secure cluster.
+
+* Open port 27017 to all nodes that will take part in the cluster.
+* Manually run an initialisation `docker run` with extra environment variables 
+that will initialise the admin user with a password (example below).
+* Manually add a `mgkey` file under `./docker/data/mongo` with the respective 
+secret (see Mongo's keyfile access control for details).
+* During the initialisation run mentioned above, we need to make two extra steps 
+within the container:
+    * Change the ownership of `mgkey` to `mongodb:mongodb`
+    * Change its permissions to 400
+* After these steps are done we can open a mongo shell on the master node and 
+run `rs.add()` in order to add the new node to the cluster.
+
+Example initialisation docker run command:
+```
+docker run \
+	--rm \
+	--name mg \
+	-p 27017:27017 \
+	-e MONGO_INITDB_ROOT_USERNAME=<admin username> \
+	-e MONGO_INITDB_ROOT_PASSWORD=<admin password> \
+	-v /home/user/skynet-webportal/docker/data/mongo/db:/data/db \
+	-v /home/user/skynet-webportal/docker/data/mongo/mgkey:/data/mgkey \
+	mongo --keyFile=/data/mgkey --replSet=skynet
+```
+Regular docker run command:
+```
+docker run \
+	--rm \
+	--name mg \
+	-p 27017:27017 \
+	-v /home/user/skynet-webportal/docker/data/mongo/db:/data/db \
+	-v /home/user/skynet-webportal/docker/data/mongo
+```
+Cluster initialisation mongo command:
+```
+rs.initiate(
+  {
+    _id : "skynet",
+    members: [
+      { _id : 0, host : "helsinki.siasky.net:27017" },
+      { _id : 1, host : "us-va-1.siasky.net:27017" },
+    ]
+  }
+)
+```
+
 ## Contributing
 
 ### Testing Your Code