sql/schemachanger: support ALTER TABLE ... ALTER COLUMN ... [ADD | SET] ... IDENTITY in declarative schema changer #142918
Description
This tracks support for statements such as ALTER TABLE t ALTER COLUMN c ADD GENERATED ALWAYS AS IDENTITY (sequence_options) and ALTER TABLE t ALTER COLUMN c SET GENERATED ALWAYS AS IDENTITY in the declarative schema changer.
Support for ADD COLUMN ... IDENTITY was added in #139135. This change will have some similar parts, but for modifying an existing column.
Jira issue: CRDB-48584