Leverage PostgreSQL count for study group size

app/models/study_group.rb

@@ -11,6 +11,10 @@ class StudyGroup < ApplicationRecord
     external_users + internal_users
   end
 
+  def user_count
+    external_users.count + internal_users.count
+  end
+
   def to_s
     if name.blank?
       "StudyGroup " + id.to_s

app/views/study_groups/index.html.slim

@@ -25,7 +25,7 @@ h1 = StudyGroup.model_name.human(count: 2)
           td
             code = group.external_id
           td = link_to_if(policy(group.consumer).show?, group.consumer, group.consumer)
-          td = group.users.count
+          td = group.user_count
           td = link_to(t('shared.show'), group) if policy(group).show?
           td = link_to(t('shared.edit'), edit_study_group_path(group)) if policy(group).edit?
           td = link_to(t('shared.destroy'), group, data: {confirm: t('shared.confirm_destroy')}, method: :delete) if policy(group).destroy?

app/views/study_groups/show.html.slim

@@ -7,7 +7,7 @@ h1
 = row(label: 'study_group.external_id') do
   code = @study_group.external_id
 = row(label: 'study_group.consumer', value: link_to_if(policy(@study_group).show?, @study_group.consumer, @study_group.consumer))
-= row(label: 'study_group.member_count', value: @study_group.users.count)
+= row(label: 'study_group.member_count', value: @study_group.user_count)
 
 
 h2.mt-4 = t('activerecord.attributes.study_group.members')