How to write data from another field into a ManyToMany field automatically?

Question

Django

There is a 'Project' model with 'managers' and 'members' fields, which have a ManyToManyField field type .
I'm trying to make it so that when filling in the 'managers' field, the records from this field are automatically duplicated or recorded in the 'members' field. I display only the 'managers' field in the admin panel. After creating the Project object, the 'members' field is empty in the database. How can this problem be solved? Here's what I've done so far:
models.py :

class Project(models.Model):
      ***
      managers = models.ManyToManyField(User, related_name='managers')
      members = models.ManyToManyField(User, related_name='members')

      def save(self, *args, **kwargs):
          if self.id:
             for manager in self.managers.all():
                if manager not in self.members.all():
                    self.members.add(manager)
           super(Project, self).save(*args, **kwargs)

I also tried the following in the admin panel itself, but to no avail:
admin.py :

class ProjectAdminForm(ModelForm):
    class Meta:
        model = Project
        fields = 'managers'

    def clean(self):
        members = self.cleaned_data['members']
        managers = list(self.cleaned_data['managers'])

        for manager in managers:
            if manager not in members:
                members.append(manager)

        self.cleaned_data['members'] = members

        return self.cleaned_data


class ProjectAdmin(admin.ModelAdmin):
    model = Project
    form = ProjectAdminForm

admin.site.register(Project, ProjectAdmin)

Answer 1

There is no need to duplicate
There are several solutions
- make a method in the model to display members + managers

class Project(models.Model):
      # ***
      def members_dict(self):
              return { 'basic_members': self.members, 'managers': self.managers}

- make a separate model and link the user, the project and his role in it there

class ProjectMembers(models.Model):
      member = ForeignKey(Member)
      progect = ForeignKey(Progect)
      is_manager = BooleanField(default=False)