Feature Suggestion: Add our own client's fields

I was trying out the plugin and noticed that there's no way to add our own fields to the client profile, at least from the backend.

For example, a pet store that have pet grooming services need to include the name of the pet, age, weight and breed fields the first time a registered client makes an appointment.

Im sure there's much more situations where the owner having the possibility to add their own field in order to capture client's information would be an important feature.

Thanks for the consideration.