+ Sets the message application id.
+
+ The codec engine could be configured to force a stack selection based in this field value: see #selectStackWithApplicationId.
+ In multistack applications (which also shall be monothreaded), you only have to take care about how to apply this method: the thing
+ is that you must not interleave message builds which belongs to different stacks. For example, you could think about setting the
+ message header for message A using stack A. Then, start to add the message header fields for a second message B using another stack B.
+ Following you would add the message A avps, but then, the stack is not going to be automatically changed (this is only done through this
+ method). The result could be unexpected when adding/encoding messages with a dictionary which does not correspond.
+
+ @warning do not interleave build/encode operations between different messages which uses different stacks over the same codec engine.
+ It seems common sense, but it is not bad to advice about this.
+