feat(v4): Add API to fetch aggregate reports for inboxes (#10604)

The Inbox Overview section is being updated to offer a more detailed
report, showing an overall view of the account grouped by inboxes. To
view detailed reports and access specific graphs for individual inboxes,
click on the inbox name to navigate to its dedicated report page.

---------

Co-authored-by: Sojan Jose <sojan@pepalo.com>

spec/builders/v2/reports/inbox_summary_builder_spec.rb

@@ -0,0 +1,101 @@
+require 'rails_helper'
+
+RSpec.describe V2::Reports::InboxSummaryBuilder do
+  let(:account) { create(:account) }
+  let(:i1) { create(:inbox, account: account) }
+  let(:i2) { create(:inbox, account: account) }
+  let(:params) do
+    {
+      business_hours: business_hours,
+      since: 1.week.ago.beginning_of_day,
+      until: Time.current.end_of_day
+    }
+  end
+  let(:builder) { described_class.new(account: account, params: params) }
+
+  before do
+    c1 = create(:conversation, account: account, inbox: i1, created_at: 2.days.ago)
+    c2 = create(:conversation, account: account, inbox: i2, created_at: 1.day.ago)
+    c2.resolved!
+    create(:reporting_event, account: account, conversation: c2, inbox: i2, name: 'conversation_resolved', value: 100, value_in_business_hours: 60,
+                             created_at: 1.day.ago)
+    create(:reporting_event, account: account, conversation: c1, inbox: i1, name: 'first_response', value: 50, value_in_business_hours: 30,
+                             created_at: 1.day.ago)
+    create(:reporting_event, account: account, conversation: c1, inbox: i1, name: 'reply_time', value: 30, value_in_business_hours: 10,
+                             created_at: 1.day.ago)
+    create(:reporting_event, account: account, conversation: c1, inbox: i1, name: 'reply_time', value: 40, value_in_business_hours: 20,
+                             created_at: 1.day.ago)
+  end
+
+  describe '#build' do
+    subject(:report) { builder.build }
+
+    context 'when business hours is disabled' do
+      let(:business_hours) { false }
+
+      it 'includes correct stats for each inbox' do
+        expect(report).to eq(
+          [
+            {
+              id: i1.id,
+              conversations_count: 1,
+              resolved_conversations_count: 0,
+              avg_resolution_time: nil,
+              avg_first_response_time: 50.0,
+              avg_reply_time: 35.0
+            }, {
+              id: i2.id,
+              conversations_count: 1,
+              resolved_conversations_count: 1,
+              avg_resolution_time: 100.0,
+              avg_first_response_time: nil,
+              avg_reply_time: nil
+            }
+          ]
+        )
+      end
+    end
+
+    context 'when business hours is enabled' do
+      let(:business_hours) { true }
+
+      it 'uses business hours values for calculations' do
+        expect(report).to eq(
+          [
+            {
+              id: i1.id,
+              conversations_count: 1,
+              resolved_conversations_count: 0,
+              avg_resolution_time: nil,
+              avg_first_response_time: 30.0,
+              avg_reply_time: 15.0
+            }, {
+              id: i2.id,
+              conversations_count: 1,
+              resolved_conversations_count: 1,
+              avg_resolution_time: 60.0,
+              avg_first_response_time: nil,
+              avg_reply_time: nil
+            }
+          ]
+        )
+      end
+    end
+
+    context 'when there is no data for an inbox' do
+      let!(:empty_inbox) { create(:inbox, account: account) }
+      let(:business_hours) { false }
+
+      it 'returns nil values for metrics' do
+        expect(report).to include(
+          id: empty_inbox.id,
+          conversations_count: 0,
+          resolved_conversations_count: 0,
+          avg_resolution_time: nil,
+          avg_first_response_time: nil,
+          avg_reply_time: nil
+        )
+      end
+    end
+  end
+end