Add documentation for connect external store node (#87)

* Add documentation for connect external store node

* add new page to summary.md

src/SUMMARY.md

@@ -6,4 +6,5 @@
 - [Connect external full node](./connect-full-node.md)
 - [Connect external spam node](./connect-spam-node.md)
 - [Connect external light node](./connect-light-node.md)
+- [Connect external store node](./connect-store-node.md)
 - [Register memberships](./register-memberships.md)

src/connect-store-node.md

@@ -0,0 +1,52 @@
+# Connect external store node
+
+One or more external store nodes can be connected to the waku-simulator network by using configuration similar to that shown below. The store node(s) can use the DB as backend from an existing staging or production system DB or a custom one. When connecting to any DB ensure that the `store-message-retention-policy` matches that of the system.
+The staticnode that the store node connects to can be any existing node in the waku-simulator network, alternatively use the discv5 configuration.
+
+```bash
+ --discv5-discovery=true \
+ --discv5-enr-auto-update=True \
+ --discv5-bootstrap-node=BOOTSTRAP_ENR\
+```
+
+The store node can be queried via the [waku rest API]( https://waku-org.github.io/waku-rest-api/#get-/store/v3/messages).
+An easy way to find a message hash to query is by checking the store node logs for the `message archived` message:
+
+```bash
+docker logs nwaku_storenode_1 | grep -i "message archived"
+```
+The store node will need to have log-level set to DEBUG for this logging to be available.
+
+The [message-finder](https://github.com/waku-org/message-finder) tool could also be useful for store node testing.
+
+
+```bash
+docker run -it --network waku-simulator_simulation --name nwaku_storenode_1 -d harbor.status.im/wakuorg/nwaku:latest \
+    --relay=true\
+    --rest=true\
+    --rest-address=0.0.0.0\
+    --rest-port=8645\
+    --log-level=DEBUG\
+    --pubsub-topic=/waku/2/rs/66/0\
+    --cluster-id=66\
+    --metrics-server=true\
+    --discv5-discovery=true\
+    --discv5-enr-auto-update=true\
+    --store=true\
+    --store-message-db-url=<e.g. postgres://pguser:[email protected]:5432/postgres>\
+    --store-message-retention-policy=size:120GB\
+    --staticnode=/ip4/0.0.0.0/tcp/60000/p2p/16Uiu2HAmC8Fe4Egsq6AKubmBPr52TQmwc26yoCkszwo6dfQncZ4m\
+    --nodekey=5978783f8b1a16795032371fff7a526af352d9dca38179af7d71c0122942fa20
+
+```
+
+
+
+🎯**Goals**:
+
+- Connect a store node(s) to the network for ad hoc store protocol testing.
+- Verify that store queries get the expected results.
+
+👀**Observability**:
+
+- Check the logs of the newly connected store node, ensuring the behaviour matches the expected.