Add merge key to pipeline

[adrianbr]

Feature description

I would like to be able to use merge key without declaring a resource. Without it, using PK alone restricts the types of merges I can do

Are you a dlt user?

None

Use case

No response

Proposed solution

user tried to

 info = pipeline.run(data2, 
                    table_name="users", 
                    write_disposition="merge",
                    merge_key='ID'
                      )

Related issues

No response