cmake: Use server mode as default

Server mode is enabled, if no mode (client, server or bootstrap-server)
is selected. A warning is submitted to inform the user of Wakaama about
the default. This simplifies testing and CI.

tools/ci/run_ci.sh

@@ -151,7 +151,7 @@ function run_build() {
 
   echo "Default build"
   ${OPT_WRAPPER_CMD} cmake -GNinja -S ${OPT_SOURCE_DIRECTORY} -B build-wakaama \
-    -DWAKAAMA_MODE_SERVER=ON -DWAKAAMA_PLATFORM=POSIX ${CMAKE_ARGS}
+    -DWAKAAMA_PLATFORM=POSIX ${CMAKE_ARGS}
   ${OPT_WRAPPER_CMD} cmake --build build-wakaama
 
   # CMake presets

wakaama.cmake

@@ -9,6 +9,14 @@ option(WAKAAMA_MODE_SERVER "Enable LWM2M Server interfaces" OFF)
 option(WAKAAMA_MODE_BOOTSTRAP_SERVER "Enable LWM2M Bootstrap Server interfaces" OFF)
 option(WAKAAMA_MODE_CLIENT "Enable LWM2M Client interfaces" OFF)
 
+if(NOT WAKAAMA_MODE_SERVER
+   AND NOT WAKAAMA_MODE_BOOTSTRAP_SERVER
+   AND NOT WAKAAMA_MODE_CLIENT
+)
+    message(WARNING "No mode selected. Defaulting to 'WAKAAMA_MODE_SERVER'")
+    set(WAKAAMA_MODE_SERVER ON)
+endif()
+
 # Client
 option(WAKAAMA_CLIENT_INITIATED_BOOTSTRAP "Enable client initiated bootstrap support in a client" OFF)
 option(WAKAAMA_CLIENT_LWM2M_V_1_0 "Restrict the client code to use LwM2M version 1.0" OFF)