Improvement: Support mapping of more complex object fields

[zakhtar1998]

Hello developers,

I have a complex elasticsearch mapping where one of my geo_point fields are within other fields e.g. user_location.resolved_location.geometry and when i specified this in the mapping of koop, it would not run successfully. Instead, i had to move the necessary fields outside on the top level so that i can use geometry only in the mapping and get koop to work.

Do you think this feature is something that can be incorporated?