Add mermaid diagram to the HA guide

docs/pages/deploy-a-cluster/high-availability.mdx

@@ -45,8 +45,57 @@ Infrastructure components include:
   credential provisioner will need to manage DNS records to demonstrate control
   over your domain name.
 
-![Diagram of a high-availability Teleport
-architecture](../../img/deploy-a-cluster/teleport-ha-architecture.png)
+{/*
+The block of &nbsp is there to push the subgraph label out of the way of the
+diagram lines. This is a hacky solution to https://github.com/mermaid-js/mermaid/issues/1209
+*/}
+
+```mermaid
+flowchart
+   subgraph public[Public Network]
+     Developers
+   end
+
+   subgraph private[Private Network]
+     server1[Teleport Service]
+     server2[Teleport Service]
+     server3[Teleport Service]
+   end
+
+   Developers & server1 & server2 & server3 --> lb1[Load Balancer]
+   lb1 --> proxies
+
+   subgraph teleport[Private Network &nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp]
+     subgraph proxies[Proxy Service Pool]
+       tp1[Teleport Proxy Service]
+       tp2[Teleport Proxy Service]
+     end
+
+     proxies --> lb2[Load Balancer]
+
+     subgraph auth[Auth Service Pool]
+       ta1[Teleport Auth Service]
+       ta2[Teleport Auth Service]
+    end
+
+    lb2-->auth
+
+    auth-->kv[Key/Value Store]
+    auth-->os[Object Store]
+   end
+
+classDef teleportColor fill:#844cff,color:#fff
+classDef nestedSub fill:#fff
+class proxies nestedSub
+class auth nestedSub
+class server1 teleportColor
+class server2 teleportColor
+class server3 teleportColor
+class tp1 teleportColor
+class tp2 teleportColor
+class ta1 teleportColor
+class ta2 teleportColor
+```
 
 ## Layer 4 load balancers