Exclude specific properties from generation-related stuff

[y9vad9]

Is your feature request related to a problem? Please describe. I'm using implier for generating database-related entities. My case is to not generate mutable property of identifier (I am not supposed to change it), but to make other properties mutable.

Describe the solution you'd like Probably, we need to have annotation for such stuff. For example ShouldNotMutate or using existing Immutable annotation.