rpc: use enum instead of string for filter type

Author: w0xlt

src/rpc/blockchain.cpp

@@ -2177,7 +2177,7 @@ static RPCHelpMan getblockfilter()
                 "\nRetrieve a BIP 157 content filter for a particular block.\n",
                 {
                     {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The hash of the block"},
-                    {"filtertype", RPCArg::Type::STR, RPCArg::Default{"basic"}, "The type name of the filter"},
+                    {"filtertype", RPCArg::Type::STR, RPCArg::Default{BlockFilterTypeName(BlockFilterType::BASIC)}, "The type name of the filter"},
                 },
                 RPCResult{
                     RPCResult::Type::OBJ, "", "",
@@ -2192,7 +2192,7 @@ static RPCHelpMan getblockfilter()
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
     uint256 block_hash = ParseHashV(request.params[0], "blockhash");
-    std::string filtertype_name = "basic";
+    std::string filtertype_name = BlockFilterTypeName(BlockFilterType::BASIC);
     if (!request.params[1].isNull()) {
         filtertype_name = request.params[1].get_str();
     }