comp AP gateway: message conversion:

Convert direct AP items to XMPP `<message>` stanzas, and vice versa.
Documentation will follow soon to explain the behaviour.

rel 366

sat/plugins/plugin_comp_ap_gateway/constants.py

@@ -29,6 +29,8 @@ TYPE_FOLLOWING = "following"
 TYPE_ITEM = "item"
 MEDIA_TYPE_AP = "application/activity+json"
 NS_AP_PUBLIC = "https://www.w3.org/ns/activitystreams#Public"
+# 3 values can be used, see https://www.w3.org/TR/activitypub/#public-addressing
+PUBLIC_TUPLE = (NS_AP_PUBLIC, "as:Public", "Public")
 # mapping from AP metadata to microblog data
 AP_MB_MAP = {
     "content": "content_xhtml",