gcoap: add gcoap_get_event_queue() to use event API

sys/include/net/gcoap.h

@@ -872,6 +872,16 @@ typedef struct {
  */
 kernel_pid_t gcoap_init(void);
 
+/**
+ * @brief   Get a pointer to the internal gcoap event queue, to offload tasks to the gcoap thread
+ *          using RIOT's event API
+ *
+ * @warning     Beware to only use the event API on it.
+ *
+ * @return  Event queue pointer
+ */
+event_queue_t *gcoap_get_event_queue(void);
+
 /**
  * @brief   Starts listening for resource paths
  *

sys/net/application_layer/gcoap/gcoap.c

@@ -26,6 +26,7 @@
 #include <string.h>
 
 #include "assert.h"
+#include "event.h"
 #include "net/coap.h"
 #include "net/gcoap.h"
 #include "net/gcoap/forward_proxy.h"
@@ -1981,6 +1982,11 @@ void gcoap_forward_proxy_post_event(void *arg)
     event_post(&_queue, arg);
 }
 
+event_queue_t *gcoap_get_event_queue(void)
+{
+    return &_queue;
+}
+
 /* separate response API */
 
 int gcoap_resp_prepare_separate(gcoap_separate_response_ctx_t *ctx,