First of all, thanks for porting this useful mod to 3.1. I will definitely use it.
Now, I have found what might be a problem in a 3.0.x to 3.1.x situation.
If you follow exactly the "official" instructions on how to migrate, you end up losing all of your data, specially the record. So, I decided to keep both the phpbb 3.0 table and the 3.0 config variables for WWH, and then, attempted the migration.
It went apparently well, BUT in the migration of the module, there was one (relatively important) problem: the WWH category and module were NOT recreated (these MUST be removed in the 3.0 cleanup prior to attempting the migtation, and is done automatically by the STK). So I had to manually create both category and module.
In my view, this is a problem in the migration file (1_2_1 specifically), as the only check for "effectively installed" is the existence of ONE config variable, nothing else. So, should I had kept the config vars, but not the DB table, the module would be totally unoperative, and most probably would create errors. And definitely, the module is not created, as this migration file did not run at all. Not sure what is the best way to set up these migrations files, but I would probably separate the creation of the table and the module into its own migration files, checking for the existence of either before the creation in each case.
The problem is currently solved for me, but I think this should be fixed before moving to RC/CDB.
Thanks a lot,
PS: I opened an issue in GitHub