Currently villagers can change professions until traded with, could we please have a boolean value that can be checked in say the Merchant object?

Example:    A unemployed villager encounters a lectern, he becomes a librarian.   If that villager trades with a player he becomes a librarian permanently unless he dies.    However; if the villager never trades with a player and the lectern is destroyed he reverts back to a normal villager, until he encounters a new workstation.

Suggest adding a flag to the Merchant to lock in their profession which would prevent them from reverting, or if a Merchant IS locked in, clearing the flag would allow them to revert and change jobs.    This would also allow plugins to reset the villagers path without destroying the entity and spawning a new one (once it's locked in).