rpc: Update getHealth documentation

static/openrpc.json

@@ -353,6 +353,18 @@
             "status": {
               "type": "string",
               "description": "\"healthy\""
+            },
+            "latestLedger": {
+              "type": "number",
+              "description": "Most recent known ledger sequence"
+            },
+            "oldestLedger": {
+              "type": "number",
+              "description": "Oldest ledger sequence kept in history"
+            },
+            "ledgerRetentionWindow": {
+              "type": "number",
+              "description": "Maximum retention window configured. When the window is full: ledgerRetentionWindow = latestLedger - oldestLedger"
             }
           }
         }
@@ -365,7 +377,10 @@
           "result": {
             "name": "getHealthResult",
             "value": {
-              "status": "healthy"
+              "status": "healthy",
+              "latestLedger": 51583040,
+              "oldestLedger": 51565760,
+              "ledgerRetentionWindow": 17280
             }
           }
         }