Use "true" and "false" for multipart/form-data booleans

Do not use "1" and "0" implicitly
Fixes #9903

Author: cipold

modules/swagger-codegen/src/main/resources/cpprest/apiclient-header.mustache

@@ -36,6 +36,7 @@ public:
     void setConfiguration(std::shared_ptr<ApiConfiguration> configuration);
 
     static utility::string_t parameterToString(utility::string_t value);
+    static utility::string_t parameterToString(bool value);
     static utility::string_t parameterToString(int32_t value);
     static utility::string_t parameterToString(int64_t value);
     static utility::string_t parameterToString(float value);

modules/swagger-codegen/src/main/resources/cpprest/apiclient-source.mustache

@@ -31,6 +31,14 @@ utility::string_t ApiClient::parameterToString(utility::string_t value)
 {
     return value;
 }
+
+utility::string_t ApiClient::parameterToString(bool value)
+{
+    std::stringstream valueAsStringStream;
+    valueAsStringStream << (value ? "true" : "false");
+    return utility::conversions::to_string_t(valueAsStringStream.str());
+}
+
 utility::string_t ApiClient::parameterToString(int64_t value)
 {
 	std::stringstream valueAsStringStream;