auth_rx - correct handling of permissions when user is global admin

* there are two king of administrators: those that have many
  of the privilegies and the user that are pointed in config file,
  auth_rx never initialized this from zero cos always assumed
  a starting point as migration, so never need or really detect
  who are the admin of the server, cos after migration the admin
  already has previous privilegies from plain db file.
* override all the possible handlers with right detection of the
  admin user from the config file, on admin detected, no matter
  what .. give it all the (on fly) privilegies currently on server
* still a privilegied user at this commit can erase the admin
  or change the password if have also enought privilegies
* WARNING: this commit will depends of the previusly commit
  as of 2aef6adf19 for right
  admin name detection.
* fix engine detection for 5.4 due callbacks handler
* wrongly invoked register_on_authplayer over 5.0+ engines

mods/auth_rx/init.lua

@@ -24,7 +24,7 @@ local auth_filter = AuthFilter( world_path, "greenlist.mt" )
 local auth_db = AuthDatabase( world_path, "auth.db" )
 local auth_watchdog = AuthWatchdog( )
 local is_50 = minetest.has_feature("object_use_texture_alpha")
-local is_54 = minetest.has_feature("object_use_texture_alpha")
+local is_54 = minetest.has_feature("direct_velocity_on_players")
 
 if is_50 then
 	if minetest.register_on_auth_fail then
@@ -128,15 +128,15 @@ end )
 minetest.register_authentication_handler( {
 	-- translate old auth hooks to new database backend
 	get_auth = function( username )
+		minetest.log( "verbose" , "[auth_rx] get_auth handler access to some resource for " .. username )
 		local rec = auth_db.select_record( username )
 		if rec then
 			local assigned_privs = rec.assigned_privs
 
 			if get_minetest_config( "name" ) == username then
 				-- grant server operator all privileges
-				-- (TODO: implement as function that honors give_to_admin flag)
 				assigned_privs = { }
-				for priv in pairs( core.registered_privileges ) do
+				for priv in pairs( minetest.registered_privileges ) do
 					table.insert( assigned_privs, priv )
 				end
 			end
@@ -145,28 +145,52 @@ minetest.register_authentication_handler( {
 		end
 	end,
 	create_auth = function( username, password )
-		if auth_db.create_record( username, password ) then
+		minetest.log( "verbose" , "[auth_rx] create_auth handler new user over server for " .. username )
-			auth_db.set_assigned_privs( username, get_default_privs( ) )
+		local rec = auth_db.create_record( username, password )
-			minetest.log( "info", "Created player '" .. username .. "' in authentication database" )
+		if rec then
+			local assigned_privs = get_default_privs( )
+
+			if get_minetest_config( "name" ) == username then
+				-- grant server operator all privileges
+				assigned_privs = { }
+				for priv in pairs( minetest.registered_privileges ) do
+					table.insert( assigned_privs, priv )
+				end
+			end
+
+			auth_db.set_assigned_privs( username, assigned_privs )
 		end
 	end,
 	delete_auth = function( username )
-		if auth_db.delete_record( username ) then
+		minetest.log( "verbose" , "[auth_rx] delete_auth handler for " .. username )
+		-- server operator's privileges are immutable
+		if get_minetest_config( "name" ) ~= username then
+			local rec =  auth_db.delete_record( username )
+			if rec then
 				minetest.log( "info", "Deleted player '" .. username .. "' in authenatication database" )
 			end
+		end
 	end,
 	set_password = function ( username, password )
-		if auth_db.set_password( username, password ) then
+		minetest.log( "verbose" , "[auth_rx] set_password handler for " .. username )
+		local rec =  auth_db.set_password( username, password )
+		if rec then
 			minetest.log( "info", "Reset password of player '" .. username .. "' in authentication database" )
 		end
 	end,
 	set_privileges = function ( username, privileges )
+		minetest.log( "verbose" , "[auth_rx] set_privileges handler grants for " .. username )
+		local assigned_privs = pack_privileges( privileges )
 		-- server operator's privileges are immutable
-		if get_minetest_config( "name" ) == username then return end
+		if get_minetest_config( "name" ) == username then
+			assigned_privs = { }
+			for priv in pairs( minetest.registered_privileges ) do
+				table.insert( assigned_privs, priv )
+			end
+		end
 
-		if auth_db.set_assigned_privs( username, pack_privileges( privileges ) ) then
+		if auth_db.set_assigned_privs( username, assigned_privs ) then
 			minetest.notify_authentication_modified( username )
-			minetest.log( "info", "Reset privileges of player '" .. username .. "' in authentication database" )
 		end
 	end,
 	record_login = function ( ) end,