Where can I find the Client management application service for ABP? I am currently using V3.2, but I can't find the implementation anywhere on GitHub.
According to the documentation: https://docs.abp.io/en/commercial/3.2/modules/identity-server there should be a class ApiResourceAppService but that doesn't seem to exist either and the ClientAppService seems to be missing even from the documentation.
I would like to add client management to my application and therefor I want to overwrite the ABP implementation and add my custom logic there.
The documents you have shared is commercial documentation.
IdentityServer module containtains the domain logic. There is also a commercial module named IdentityServer UI which contains the application service implementations and the UI of identity server.
If you already own commercial license, you can check support for how to override existing modules. Otherwise, you need to introduce and implement the whole identityserver UI logic yourself.
You can also check abp free and commercial modules comparison.