refactor(docs): Improve the documentation of async operations

include/open62541/server.h

@@ -1374,22 +1374,22 @@ UA_Server_AccessControl_allowHistoryUpdateDeleteRawModified(UA_Server *server,
 #endif // UA_ENABLE_HISTORIZING
 
 /**
-* .. _async_methods:
+* .. _async_operations:
 *
-* Async Methods
-* -------------
-* Sample on working with async method calls
-* Check client_method_async and tutorial_server_method_async for working samples.
+* Async Operations
+* ----------------
+* Some operations (such as reading out a sensor that needs to warm up) can take
+* quite some time. In order not to block the server during such an operation, it
+* can be "outsourced" to a worker thread.
 *
-* Minimal Server:
+* Take the example of a CallRequest. It is split into the individual method call
+* operations. If the method is marked as async, then the operation is put into a
+* queue where it is be retrieved by a worker. The worker returns the result when
+* ready. See the examples in ``/examples/tutorial_server_method_async.c`` for
+* the usage.
 *
-* - Create a method node
-* - mark as async: ``UA_Server_MethodNodeAsync``
-* - set callback to be notified: ``config->asyncOperationNotifyCallback = ...``
-* - fetch MethodCall: ``UA_Server_GetNextAsyncMethod``
-* - execute Method: e.g. UA_Server_call(UA_Server*, UA_CallMethodRequest*)
-* - pass back the result: ``UA_Server_SetAsyncMethodResult``
-* - free memory used: free UA_CallMethodResult */
+* Note that the operation can time out (see the asyncOperationTimeout setting in
+* the server config) also when it has been retrieved by the worker. */
 
 #if UA_MULTITHREADING >= 100
 
@@ -1417,20 +1417,19 @@ typedef union {
     /* UA_StatusCode writeResult; */
 } UA_AsyncOperationResponse;
 
-/* Get and remove next Method Call Request
+/* Get the next async operation
  *
  * @param server The server object
  * @param type The type of the async operation
  * @param request Receives pointer to the operation
  * @param context Receives the pointer to the operation context
- * @return UA_FALSE if queue is empty, UA_TRUE else
- * Note: Timeout is doubled for requests which already got fetched by worker via UA_Server_getAsyncOperation */
+ * @return false if queue is empty, true else */
 UA_Boolean UA_EXPORT
 UA_Server_getAsyncOperation(UA_Server *server, UA_AsyncOperationType *type,
                             const UA_AsyncOperationRequest **request,
                             void **context);
 
-/* Worker submits Method Call Response
+/* Submit the next async operation
  *
  * @param server The server object
  * @param response Pointer to the operation result