Create a way to extract common connector_properties to dbt_project.yml

[gliter]

Dbt allows to move common key from config into dbt_project.yml the problem is it only allows to move there entire key and when overriding in models, seeds, sources it overwrite entire key. This is a problem for connector_properties which is a dictionary.

My initial proposal would be to add separate key like "default_connector_properties" that could be used in dbt_project.yml and it would get merged with connector_properties.