Add Reporting Mode

* Add a new operating mode to rippled called reporting mode
* Add ETL mechanism for a reporting node to extract data from a p2p node
* Add new gRPC methods to faciliate ETL
* Use Postgres in place of SQLite in reporting mode
* Add Cassandra as a nodestore option
* Update logic of RPC handlers when running in reporting mode
* Add ability to forward RPCs to a p2p node

src/ripple/protocol/impl/ErrorCodes.cpp

@@ -74,6 +74,9 @@ constexpr static ErrorInfo unorderedErrorInfos[]{
      "Destination issuer is malformed."},
     {rpcEXCESSIVE_LGR_RANGE, "excessiveLgrRange", "Ledger range exceeds 1000."},
     {rpcFORBIDDEN, "forbidden", "Bad credentials."},
+    {rpcFAILED_TO_FORWARD,
+     "failedToForward",
+     "Failed to forward request to p2p node"},
     {rpcHIGH_FEE, "highFee", "Current transaction fee exceeds your limit."},
     {rpcINTERNAL, "internal", "Internal error."},
     {rpcINVALID_LGR_RANGE, "invalidLgrRange", "Ledger range is invalid."},
@@ -98,6 +101,9 @@ constexpr static ErrorInfo unorderedErrorInfos[]{
      "You don't have permission for this command."},
     {rpcNO_PF_REQUEST, "noPathRequest", "No pathfinding request in progress."},
     {rpcPUBLIC_MALFORMED, "publicMalformed", "Public key is malformed."},
+    {rpcREPORTING_UNSUPPORTED,
+     "reportingUnsupported",
+     "Requested operation not supported by reporting mode server"},
     {rpcSIGNING_MALFORMED,
      "signingMalformed",
      "Signing of transaction is malformed."},