Tonic Structural release notes

Made the following changes to the Finnish Personal Identity Code generator:

• The generator now preserves uniqueness, and can be used on unique and primary-key columns.

• The century indicator in each generated code now mirrors the source value instead of being spread evenly across every indicator letter. This ensures that common indicators (+, -, A) remain common, and that rare reform letters only appear when the source uses them.

• During data generation, Structural warns when the sampled values fall outside of the chosen birth-date range or use indicators that the range cannot represent. Structural drops those rows instead of writing them to the destination.