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>

enterprise/LICENSE

@@ -0,0 +1,36 @@
+The Chatwoot Enterprise license (the “Enterprise License”)
+Copyright (c) 2017-2021 Chatwoot Inc
+
+With regard to the Chatwoot Software:
+
+This software and associated documentation files (the "Software") may only be
+used in production, if you (and any entity that you represent) have agreed to,
+and are in compliance with, the Chatwoot Subscription Terms of Service, available
+at https://www.chatwoot.com/terms-of-service/ (the “Enterprise Terms”), or other
+agreement governing the use of the Software, as agreed by you and Chatwoot,
+and otherwise have a valid Chatwoot Enterprise License for for the
+correct number of user seats. Subject to the foregoing sentence, you are free to
+modify this Software and publish patches to the Software. You agree that Chatwoot
+and/or its licensors (as applicable) retain all right, title and interest in and
+to all such modifications and/or patches, and all such modifications and/or
+patches may only be used, copied, modified, displayed, distributed, or otherwise
+exploited with a valid Chatwoot Enterprise subscription for the correct
+number of user seats. Notwithstanding the foregoing, you may copy and modify
+the Software for development and testing purposes, without requiring a
+subscription. You agree that Chatwoot and/or its licensors (as applicable) retain
+all right, title and interest in and to all such modifications. You are not
+granted any other rights beyond what is expressly stated herein. Subject to the
+foregoing, it is forbidden to copy, merge, publish, distribute, sublicense,
+and/or sell the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+For all third party components incorporated into the Chatwoot Software, those
+components are licensed under the original license provided by the owner of the
+applicable component.

enterprise/app/models/enterprise/account.rb

@@ -0,0 +1,15 @@
+module Enterprise::Account
+  def usage_limits
+    {
+      agents: get_limits(:agents),
+      inboxes: get_limits(:inboxes)
+    }
+  end
+
+  private
+
+  def get_limits(limit_name)
+    config_name = "ACCOUNT_#{limit_name.to_s.upcase}_LIMIT"
+    self[:limits][limit_name.to_s] || GlobalConfig.get(config_name)[config_name] || ChatwootApp.max_limit
+  end
+end

enterprise/lib/enterprise.rb

@@ -0,0 +1,2 @@
+module Enterprise
+end