Currently, api.h includes mongo/util/modules.h in for modularity visibility macros. However, api.h will eventually be used by downstream teams, who'll have to explicitly remove the modules dependency because it's server-specific (they'll have to include that header even though their extensions are developed separately from the server).

We should only include the header if it's available

#if __has_include("mongo/util/modules.h") 
#else #define MONGO_MOD_PUB // no-op if the header is unavailable