hook_ENTITY_TYPE_insert never called Initially I wanted a list of Authors in an exposed filter (as a checkbox) but after looking into BEF (better exposed filters) it seems this isn't possible.

Instead I am trying to create a taxonomy term for each user created but have found regardless of what entity I am trying to create, the hook for insertion is never called. 

I am using xdebug and was expecting at least a single breakpoint inside one of the functions to work but it never triggers, I have cleared my cache and other preprocessing functions inside this file (bare.theme).

A few examples of functions I have tried (my theme is called "bare"):

function bare_entity_insert(Drupal\Core\Entity\EntityInterface $entity){}

function bare_user_insert(\Drupal\user\UserInterface $user) {}

function bare_entity_create(Drupal\Core\Entity\EntityInterface $entity){}

function bare_user_create(\Drupal\user\Plugin\Core\Entity\User $user){


I feel I have missed something very crucial, perhaps I can't call these functions inside a .theme file?
Yes if you're trying that in a theme then it won't work and will need to be done in a module (Obviously changing the "bare" to whatever your module name is)