Core: Validate transforms while building partition type

[aokolnychyi]

Until we store the output type of transforms, we should fail building the partition type if we hit UnknownTransform.

[aokolnychyi]

cc @RussellSpitzer @szehon-ho @jackye1995 @yyanyy @kbendick @karuppayya @rdblue

[kbendick]

This looks good to me overall. A few questions for my own understanding.

A few questions:

1. I'm assuming you're using this subset of metadata tables because they're partitioned?
2. Is there a way to add a test against a table itself (and not just the metadata tables)?

[aokolnychyi]

@kbendick, this is a follow-up to #2936 where I added Partitioning#partitionType. It is only used within these metadata tables that I added tests for. W.r.t. reading the table itself, we have TestForwardCompatibility that already covers writing and reading to a table with unknown transforms.

[yyanyy]

I guess I'm not familiar with the context, is this case only going to be hit when there's a new writer that commit partition spec to the table that contains a new transform, and the metadata tables associated with the table is read by the old reader which does not recognize this transform; and we are updating the logic for this old reader to fail gracefully?

[aokolnychyi]

@yyanyy, that's exactly the use case.

[jackye1995]

this also looks good to me

[aokolnychyi]

Thanks for reviewing, @kbendick @yyanyy @jackye1995!