[TYPO3-mvc] extbase: m:n relation between extension table and fe_users

[Matthias Nagl]

Are any examples available on how to create a (preferably bidirectional) m:n 
relation beween a table created using the extension builder and fe_users? Are 
the counting dummy fields in both tables still necessary?
I found some information on adding fields and 1:n relations to fe_users and use 
them in my extbase extension but nothing concerning m:n relations.

Many thanks!

- Matthias