Prostore::Schema
Constants
ACTIONS = [:no_action, :restrict, :cascade, :set_null, :set_default]
A foreign-key declaration (ADR-0012).
references_table is captured as a string (the target model's resolved
table name) so the schema struct does not hold a class reference.
Resolution to the actual target column happens at planner time —
references_columns may be empty when the user did not pass
references_fields:, in which case the planner resolves to the target
table's primary key.