rename api, add cc and bcc, handle multiple players

rename: src -> from, dst -> to

util/normalize.lua

@@ -0,0 +1,26 @@
+--[[
+return the field normalized (comma separated, single space)
+and add individual player names to recipient list
+--]]
+function normalize_players_and_add_recipients(field, recipients)
+    local separator = ", "
+    local pattern = "([^" .. separator .. "]+)"
+
+    -- get individual players
+    local player_set = {}
+    local order = {}
+    field:gsub(pattern, function(c)
+        if player_set[string.lower(c)] ~= nil then
+            player_set[string.lower(c)] = c
+            order[#order+1] = c
+
+            -- also sort into recipients
+            if recipients[string.lower(c)] ~= nil then
+                recipients[string.lower(c)] = c
+            end
+        end
+    end)
+
+    -- turn list of players back into normalized string
+    return table.concat(order, ", ")
+end