obfs, string: Modify to make_string

test/impl/string_obfs.cpp

@@ -1,16 +1,14 @@
 #include <string_obfs.hpp>
 #include <catch2/catch.hpp>
 
-TEST_CASE("xor string obfs", "[StringObfs]") {
-    using byte = unsigned char;
-
-    auto xor = [](byte key) constexpr {
-        return [=](char c) constexpr -> char {
-            return c ^ key;
+TEST_CASE("xor test", "[obfs::String]") {
+    auto xor = [](char key) constexpr {
+        return [=](char chr) constexpr {
+            return static_cast<char>(key ^ chr);
         };
     };
 
     REQUIRE(
-        make_stringobfs("Hello World !", xor(0x20), xor(0x20)).decode()
+        obfs::make_string("Hello World !", xor(0x20), xor(0x20)).decode()
         == std::string_view("Hello World !"));
 }