Account tx v1 api support (#874)

* Don't fail on ledger params for v1

* Different error on invalid ledger indexes for v1

* Allow forward and binary to be not bool for v1

* Minor fixes

* Fix tests

* Don't fail if input ledger index is out of range for v1

* Restore deleted test

* Fix comparison of integers with different signedness

* Updated default api version in README and example config

src/rpc/common/JsonBool.h

@@ -0,0 +1,46 @@
+#pragma once
+
+#include <boost/json/value_to.hpp>
+namespace rpc {
+
+/**
+ * @brief A wrapper around bool that allows to convert from any JSON value
+ */
+struct JsonBool
+{
+    bool value = false;
+
+    operator bool() const
+    {
+        return value;
+    }
+};
+
+inline JsonBool
+tag_invoke(boost::json::value_to_tag<JsonBool> const&, boost::json::value const& jsonValue)
+{
+    switch (jsonValue.kind())
+    {
+        case boost::json::kind::null:
+            return JsonBool{false};
+        case boost::json::kind::bool_:
+            return JsonBool{jsonValue.as_bool()};
+        case boost::json::kind::uint64:
+            [[fallthrough]];
+        case boost::json::kind::int64:
+            return JsonBool{jsonValue.as_int64() != 0};
+        case boost::json::kind::double_:
+            return JsonBool{jsonValue.as_double() != 0.0};
+        case boost::json::kind::string:
+            // Also should be `jsonValue.as_string() != "false"` but rippled doesn't do that. Anyway for v2 api we have
+            // bool validation
+            return JsonBool{!jsonValue.as_string().empty() && jsonValue.as_string()[0] != 0};
+        case boost::json::kind::array:
+            return JsonBool{!jsonValue.as_array().empty()};
+        case boost::json::kind::object:
+            return JsonBool{!jsonValue.as_object().empty()};
+    }
+    throw std::runtime_error("Invalid json value");
+}
+
+}  // namespace rpc

src/rpc/common/Specs.h

@@ -76,6 +76,18 @@ struct RpcSpec final
     {
     }
 
+    /**
+     * @brief Construct a full RPC request specification from another spec and additional fields.
+     *
+     * @param other The other spec to copy fields from
+     * @param additionalFields The additional fields to add to the spec
+     */
+    RpcSpec(const RpcSpec& other, std::initializer_list<FieldSpec> additionalFields) : fields_{other.fields_}
+    {
+        for (auto& f : additionalFields)
+            fields_.push_back(std::move(f));
+    }
+
     /**
      * @brief Processos the passed JSON value using the stored field specs.
      *