Currently the mqtt_supported_features.h is in PRIV_INCLUDE_DIRS.
So the application cannot include it.
To write application code that can be compiled with different esp-idf versions.
Now it needs to add #if gurad with checking ESP_IDF_VERSION in application code.
(And manually check if some feature actually back-ported to old ESP_IDF_VERSION)
I think a better way is to allow application to include mqtt_supported_features.h,
then the application just need to add #ifdef MQTT_SUPPORTED_FEATURE_XXX.
Currently the mqtt_supported_features.h is in PRIV_INCLUDE_DIRS. So the application cannot include it.
To write application code that can be compiled with different esp-idf versions. Now it needs to add #if gurad with checking ESP_IDF_VERSION in application code. (And manually check if some feature actually back-ported to old ESP_IDF_VERSION)
I think a better way is to allow application to include mqtt_supported_features.h, then the application just need to add #ifdef MQTT_SUPPORTED_FEATURE_XXX.