add description class

To create issues, we need descriptions. Contrary to the requirements, I go for narrow strings for now.

src/domain/CMakeLists.txt

@@ -1,5 +1,6 @@
 set(DOMAIN_SOURCES
     application_service.cpp
+    description.cpp
     domain_error.cpp
     title.cpp
     )

src/domain/description.cpp

@@ -0,0 +1,9 @@
+#include "description.hpp"
+
+using namespace fix::domain;
+
+description::description(std::string_view text) : text{text} {}
+
+std::string const& description::to_string() const {
+  return text;
+}

src/domain/description.hpp

@@ -0,0 +1,21 @@
+#ifndef FIX_SRC_DOMAIN_DESCRIPTION_HPP
+#define FIX_SRC_DOMAIN_DESCRIPTION_HPP
+
+#include <string>
+#include <string_view>
+
+#include "domain_error.hpp"
+
+namespace fix::domain {
+
+class description {
+  std::string text;
+
+public:
+  explicit description(std::string_view text);
+  std::string const& to_string() const;
+};
+
+} // namespace fix::domain
+
+#endif // FIX_SRC_DOMAIN_DESCRIPTION_HPP

test/domain/CMakeLists.txt

@@ -1,5 +1,6 @@
 set(DOMAIN_TEST_SOURCES
     application_service_test.cpp
+    description_test.cpp
     domain_error_test.cpp
     title_test.cpp
     )

test/domain/description_test.cpp

@@ -0,0 +1,28 @@
+#include <catch2/catch.hpp>
+
+#include "description.hpp"
+
+#include <string>
+#include <type_traits>
+
+using fix::domain::description;
+using namespace std::literals;
+
+TEST_CASE("Public construction of descriptions is only possible via copy, move") {
+  STATIC_REQUIRE(std::is_copy_constructible_v<description>);
+  STATIC_REQUIRE(std::is_move_constructible_v<description>);
+
+  STATIC_REQUIRE_FALSE(std::is_default_constructible_v<description>);
+}
+
+TEST_CASE("Descriptions can be created from any string") {
+  auto const description_text = GENERATE(""s, "any string"s, std::string(4000, '\1'));
+  REQUIRE_NOTHROW(description{description_text});
+}
+
+TEST_CASE("Descriptions can be converted back to strings") {
+  auto const description_text = GENERATE(
+      "some description"s, "the description:\n\t- line breaks are allowed\n\t- and other formatting as well"s);
+  auto const the_description = description{description_text};
+  CHECK(the_description.to_string() == description_text);
+}