Be more frugal about updating relationships

[jrjohnson]

Anytime an API request comes in for an endpoint we clear all of the relationships and then rebuild them from the sent data. Instead we should only change those items which have changed. This may improve some deadlock issue and will also have the benefit of only placing actual changes into the audit log. Currently every request indicates that it has changed relationships.

This might look like:

  /**
     * @param Collection $users
     */
    public function setUsers(Collection $users = null)
    {
        if (is_null($users)) {
            $this->users = new ArrayCollection();
            return;
        }

        $existingUsers = $this->getUsers();
        $usersToDelete = $existingUsers->filter(function (User $user) use ($users) {
            return !$users->contains($user);
        });
        $usersToAdd = $users->filter(function (User $user) use ($existingUsers) {
            return !$existingUsers->contains($user);
        });

        foreach ($usersToDelete as $user) {
            $this->removeUser($user);
        }

        foreach ($usersToAdd as $user) {
            $this->addUser($user);
        }
    }

Much of this can likely be generalized into a trait to limit code duplication.

[jrjohnson]

Turns out the symfony will handle this for us if we add removeer methods to each entity. Then forms will no longer call set they will just call that method.

[jrjohnson]

Fixed in #1611