The implementation is here: https://github.com/google/nomulus/tree/master/java/google/re...
And a sample domain create EPP message with an attached fee from our test suite: https://github.com/google/nomulus/blob/master/javatests/goog...
I saw that donuts has a test EPP endpoint to try nomulus. I will probably connect to it soon for some integration testing.
My only issues when using this extension:
* It's super flexible. I have to guess if a fee is an EAP fee based on the description, for example. (Registries haven't standardised on anything.)
* Querying for all operations * terms is very verbose.
* The extension itself has multiple versions. We support fee-0.5 - fee-0.8.
Said lists are imported into the system from the CSV file format that is given to registrars by this command-line tool: https://github.com/google/nomulus/blob/master/java/google/re...
By the way, can I just say as an aside, that it's so awesome that I can finally link to and discuss our code in the open (I wrote this pricing stuff under stuff).