I made this little admin/crud interface - see https://github.com/yairchu/yesod-admin-crud
It provides a simple admin interface to see data from the database, add rows, edit and delete.
The library user just has to add a route for the sub-site and a call to "mkYesodAdmin" along with his "mkPersist".
It works, but it isn't finished yet.
It lacks some stuff such as:
*Giving admin interface access only to admins.
*Selecting which part of the table to see if it has many rows.
*It doesn't look so nice. I don't know HTML/CSS..
*No support for admin interfaces for multiple different yesod apps running in same program.. This is due to a limitation of mkYesodSub or of my understanding of how to use it (?)..
I saw https://github.com/piyush-kurur/yesod-admin but I wanted something where the user doesn't need to do manual work to get the admin interface.
Cheers, Yair