feat: add users and sessions discovery

- also add clangd multi-file intellisense

include/sessions.h

@@ -0,0 +1,13 @@
+#include <sys/types.h>
+
+struct session {
+  char *name;
+  char *path;
+};
+
+struct sessions_list {
+  u_int16_t length;
+  struct session *sessions;
+};
+
+struct sessions_list *get_avaliable_sessions();

include/users.h

@@ -0,0 +1,13 @@
+#include <sys/types.h>
+
+struct user {
+  char *username;
+  char *display_name;
+};
+
+struct users_list {
+  u_int16_t length;
+  struct user *users;
+};
+
+struct users_list *get_human_users();

include/util.h

@@ -0,0 +1 @@
+void strcln(char **dest, const char *source);