Enhance the sqlite3_user_add() interface to initialize the user

authentication logic.  Add test cases for the extra argument on the
end of the authorizer callback.

FossilOrigin-Name: 842c6da8f1a62bd13a1b4089a98b0835a46a2285

src/shell.c

@@ -3445,6 +3445,7 @@ static int do_meta_command(char *zLine, ShellState *p){
       rc = 1;
       goto meta_command_exit;
     }
+    open_db(p, 0);
     if( strcmp(azArg[1],"login")==0 ){
       if( nArg!=4 ){
         fprintf(stderr, "Usage: .user login USER PASSWORD\n");