feat: Add inbox details endpoint (#5549)

This change targets the public API and is related to the Inbox with channel type API.
Exposes public inbox details under /public/api/v1/inboxes/{inbox_identifier}. This allows access to feature flags and business hours configured for the inbox.

ref: #5514

spec/controllers/public/api/v1/inbox/inboxes_controller_spec.rb

@@ -0,0 +1,18 @@
+require 'rails_helper'
+
+RSpec.describe 'Public Inbox API', type: :request do
+  let!(:api_channel) { create(:channel_api) }
+
+  describe 'GET /public/api/v1/inboxes/{identifier}' do
+    it 'is able to fetch the details of an inbox' do
+      get "/public/api/v1/inboxes/#{api_channel.identifier}"
+
+      expect(response).to have_http_status(:success)
+      data = response.parsed_body
+
+      expect(data.keys).to include('name', 'timezone', 'working_hours', 'working_hours_enabled')
+      expect(data.keys).to include('csat_survey_enabled', 'greeting_enabled', 'identity_validation_enabled')
+      expect(data['identifier']).to eq api_channel.identifier
+    end
+  end
+end