chore: Introduce enterprise edition license (#3209)

- Initialize an "enterprise" folder that is copyrighted.
- You can remove this folder and the system will continue functioning normally, in case you want a purely MIT licensed product.
- Enable limit on the number of user accounts in enterprise code.
- Use enterprise edition injector methods (inspired from Gitlab).
- SaaS software would run enterprise edition software always.

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

spec/models/account_spec.rb

@@ -21,4 +21,12 @@ RSpec.describe Account do
   it { is_expected.to have_many(:kbase_portals).dependent(:destroy_async) }
   it { is_expected.to have_many(:kbase_categories).dependent(:destroy_async) }
   it { is_expected.to have_many(:teams).dependent(:destroy_async) }
+
+  describe 'usage_limits' do
+    let(:account) { create(:account) }
+
+    it 'returns ChatwootApp.max limits' do
+      expect(account.usage_limits).to eq({ agents: ChatwootApp.max_limit, inboxes: ChatwootApp.max_limit })
+    end
+  end
 end