Request for secondary department membership

Hi all,

I know this is possible to add a secondary department membership through the Department management page (see below)

But I would like to add a Service Catalog to allow end users to request for secondary department membership.

I can see one easy solution but with too much maintenance operation :

1- crete a Service catalog : Organizational Unit,

2- Create an item for each Department

3- Create a ressource for each Department

=> each time a reog is performed I have to recreate all these objects.

I think there is a better way to do this using the built in item and ressource. On this point I'm stuck

See below What I've done :

1- Create an IT Shop UO

2- Create customers : allow anybody

3- Create a shelf and add the The two build in products : business role entitlement assignment and Business role membership

But now I'm stuck and I don't know how can I specify that these business role request can only be done on department secondary membership.

Do you know where can I specify that these requests are only for secondary department requests ?

Thanks for your help and happy new year