Add Protocol::SignedMessage struct (not done)

CMakeLists.txt

@@ -4,12 +4,12 @@ project(Sabalty)
 set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+include(FetchContent)
 
 option(BUILD_TESTING "Build tests" OFF)
 if(BUILD_TESTING)
 	enable_testing()
 
-	include(FetchContent)
 	FetchContent_Declare(
 		Catch2
       		GIT_REPOSITORY https://github.com/catchorg/Catch2.git
@@ -21,5 +21,12 @@ if(BUILD_TESTING)
     	include(Catch)
 endif()
 
+FetchContent_Declare(Sodium
+	GIT_REPOSITORY https://github.com/robinlinden/libsodium-cmake.git
+    	GIT_TAG cfebfd3da486d5a86c644c8b47067e5411c7599c # HEAD, last updated at 2026-02-28
+)
+set(SODIUM_DISABLE_TESTS ON)
+FetchContent_MakeAvailable(Sodium)
+
 add_subdirectory(Server)
 add_subdirectory(Protocol)