feat (ee): APIs to configure an auto assignment limit for inboxes (#4672)

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>

spec/enterprise/models/inbox_spec.rb

@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Inbox do
+  describe 'member_ids_with_assignment_capacity' do
+    let!(:inbox) { create(:inbox) }
+    let!(:inbox_member_1) { create(:inbox_member, inbox: inbox) }
+    let!(:inbox_member_2) { create(:inbox_member, inbox: inbox) }
+    let!(:inbox_member_3) { create(:inbox_member, inbox: inbox) }
+    let!(:inbox_member_4) { create(:inbox_member, inbox: inbox) }
+
+    before do
+      create(:conversation, inbox: inbox, assignee: inbox_member_1.user)
+      # to test conversations in other inboxes won't impact
+      create_list(:conversation, 3, assignee: inbox_member_1.user)
+      create_list(:conversation, 2, inbox: inbox, assignee: inbox_member_2.user)
+      create_list(:conversation, 3, inbox: inbox, assignee: inbox_member_3.user)
+    end
+
+    it 'validated max_assignment_limit' do
+      account = create(:account)
+      expect(build(:inbox, account: account, auto_assignment_config: { max_assignment_limit: 0 })).not_to be_valid
+      expect(build(:inbox, account: account, auto_assignment_config: {})).to be_valid
+      expect(build(:inbox, account: account, auto_assignment_config: { max_assignment_limit: 1 })).to be_valid
+    end
+
+    it 'returns member ids with assignment capacity with inbox max_assignment_limit is configured' do
+      # agent 1 has 1 conversations, agent 2 has 2 conversations, agent 3 has 3 conversations and agent 4 with none
+      inbox.update(auto_assignment_config: { max_assignment_limit: 2 })
+      expect(inbox.member_ids_with_assignment_capacity).to contain_exactly(inbox_member_1.user_id, inbox_member_4.user_id)
+    end
+
+    it 'returns all member ids when inbox max_assignment_limit is not configured' do
+      expect(inbox.member_ids_with_assignment_capacity).to eq(inbox.members.ids)
+    end
+  end
+end