first half of support for books stream

src/rpc/handlers/ServerInfo.cpp

@@ -0,0 +1,26 @@
+
+#include <backend/BackendInterface.h>
+#include <rpc/RPCHelpers.h>
+
+namespace RPC {
+
+Result
+doServerInfo(Context const& context)
+{
+    boost::json::object response = {};
+
+    auto range = context.backend->fetchLedgerRange();
+    if (!range)
+    {
+        return Status{Error::rpcNOT_READY, "rangeNotFound"};
+    }
+    else
+    {
+        response["info"] = boost::json::object{};
+        response["info"].as_object()["complete_ledgers"] =
+            std::to_string(range->minSequence) + " - " +
+            std::to_string(range->maxSequence);
+    }
+    return response;
+}
+}  // namespace RPC