pharo: Allow converting the authorization message as well

We need >>#do: as nextPutAllOn: is not called/doesn't exist in
this dialect.

callagent/authorization/SIPAuthorization.st

@@ -103,6 +103,10 @@ Object subclass: SIPAuthorization [
                         url: uri.
     ]
 
+    do: aBlock [
+        (String streamContents: [:str | self nextPutAllOn: str]) do: aBlock
+    ]
+
     nextPutAllOn: aStream [
         aStream
             nextPutAll: 'Digest username="';