Storage external on originator_envelope

[fbac]

As originator_envelope contains MLS ciphertext, we could avoid compressing it entirely by ALTER COLUMN originator_envelope SET STORAGE EXTERNAL; and avoid wasting CPU cycles.

[tylerhawkes]

If you can do this, then this column should be moved back into the main table because this will always push the data out to TOAST which will keep the main table about the same size without us having the overhead of managing another table and indexes.