James allows users to store Sieve scripts. As defined in ManageSieve RFC such storage should be limited by quotas. Hence, James allow administration of such quotas via the Command Line Client. But miss this administration aspect through webadmin.
In webadmin-data project, crete a SieveQuota route class directly calling SieveRepository to create, read and delete such quotas. Globally, and per user. You will write relevant unit tests.
You can have a look to the existing GlobalQuotaRoutes and related tests in GlobalQuotaRoutesTest.
Here is the proposed API:
Don't hesitate to ask for help on the Gitter chat.