Add pre and post validation for users that want to use their own public keys

resources/prosody-plugins/mod_auth_token.lua

 	return nil;
 end
 
+local function validate_result(session, res, error, reason)
+    if res == false then
+        log("warn",
+            "Error verifying token err:%s, reason:%s", error, reason);
+        session.auth_token = nil;
+        return res, error, reason;
+    end
+end
+
 function provider.get_sasl_handler(session)
 
 	local function get_username_from_token(self, message)
-        local res, error, reason = token_util:process_and_verify_token(session);
 
-        if (res == false) then
-            log("warn",
-                "Error verifying token err:%s, reason:%s", error, reason);
-            session.auth_token = nil;
-            return res, error, reason;
+        -- retrieve custom public key from server and save it on the session
+        local event_result = prosody.events.fire_event("pre-jitsi-authentication-fetch-key", session);
+        if event_result ~= nil then
+            validate_result(session,event_result.res, event_result.error, event_result.reason)
         end
 
+        local res, error, reason = token_util:process_and_verify_token(session);
+        validate_result(session, res, error, reason);
+
         local customUsername
             = prosody.events.fire_event("pre-jitsi-authentication", session);
 
             self.username = message;
         end
 
+        local event_result = prosody.events.fire_event("post-jitsi-authentication", session);
+        if event_result ~= nil then
+            validate_result(session,event_result.res, event_result.error, event_result.reason)
+        end
+
         return res;
 	end
 

resources/prosody-plugins/token/util.lib.lua

     end
 
     local pubKey;
-    if self.asapKeyServer and session.auth_token ~= nil then
+    if session.public_key then
+        module:log("debug","Public key was found on the session");
+        pubKey = session.public_key;
+    elseif self.asapKeyServer and session.auth_token ~= nil then
         local dotFirst = session.auth_token:find("%.");
         if not dotFirst then return nil, "Invalid token" end
         local header, err = json_safe.decode(basexx.from_url64(session.auth_token:sub(1,dotFirst-1)));