Cannot pick KEY from nested Avro field

[SamirHafez]

KSQL introduced the ability to handle nested structures for Avro records. The problem in when creating a TABLE, the KEY field provided in the WITH clause doesn't support nested fields.

Having the structure (pseudo-avro):

{"name": "hello!",
 "inner": {"id", "12345"}}

It's not possible to do:
CREATE TABLE <X> WITH (..., KEY='inner.id')

To get around this atm, it would be required to create a STREAM from the topic, then another STREAM which surfaces the required field to the root of the structure. Then it would be possible to simply use it for creating a TABLE;

[miguno]

And to add to this: It's not just Avro, it's also a problem for JSON afaict.

[rmoff]

This should be addressed in the wider issue here #824