Creates a new map and puts the given headers under the key
{@link NativeMessageHeaderAccessor#NATIVE_HEADERS NATIVE_HEADERS NATIVE_HEADERS NATIVE_HEADERS}.
effectively treats the input header map as headers to be sent out to the
destination.
<p>However if the given headers already contain the key
{@code NATIVE_HEADERS NATIVE_HEADERS} then the same headers instance is
returned without changes.
<p>Also if the given headers were prepared and obtained with
{@link SimpMessageHeaderAccessor#getMessageHeaders()} then the same headers
instance is also returned without changes.
Creates a new map and puts the given headers under the key {@link NativeMessageHeaderAccessor#NATIVE_HEADERS NATIVE_HEADERS NATIVE_HEADERS NATIVE_HEADERS}. effectively treats the input header map as headers to be sent out to the destination. <p>However if the given headers already contain the key {@code NATIVE_HEADERS NATIVE_HEADERS} then the same headers instance is returned without changes. <p>Also if the given headers were prepared and obtained with {@link SimpMessageHeaderAccessor#getMessageHeaders()} then the same headers instance is also returned without changes.