[Proposal]: Select / Drop Transformations

[norberttech]

Describe the Proposal

In order to improve DX of to_transformation loader we should create some more predefined implementations of Transformation interface.

Transformation interface can be easily use through df()->with() or df()->transform()

Transformations should be implemented in src/core/etl/src/Flow/ETL/Transformation location and should be cover only by simple integration tests (they are anyway using scalar functions under the hood that are properly unit tested).

Last but not least we should create a documentation page documentation/components/core/transformations.md that will explains what are transformations and how they can be used (for example with to_transformation loader)

API Adjustments

DSL Functions

select(string|Reference ...$entries);
drop(string|Reference ...$entries); 

Additionally there are few more predefined transformations like that are not yet covered in DSL so we should add them:

batch_size()
add_row_index()
limit()
mask_columns() 

Are you intenting to also work on proposed change?

None

Are you interested in sponsoring this change?

None

Integration & Dependencies

No response