Investigate replication of column additions in structs

_As a user of CircusTrain_
_I'd like to know if I can change struct columns without breaking replication_


Acceptance Criteria:
* Write an integration test for the following scenario. 
  - Table (with a column of type struct) is replicated
  - column is update on source to contain extra columns. (struct type change)
  - Type change is replicated to target table correctly.