docs: add ADR for pulling cc code out of platform

docs/decisions/0008-pull-commerce-coordinator-code-out-of-platform.rst

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+8. Pull Commerce Coordinator related code out of edx-platform
+#############################################################
+
+Status
+******
+
+**Draft**
+
+Context
+*******
+
+Kyle from Axim marked Commerce Coordinator related code in edx-platform as `business-related`. For Reference see `PR`_
+
+.. _PR: https://github.com/openedx/edx-platform/pull/35203
+
+As a result of this we need to pull out all the references of `commerce-coordinator` from `edx-platform` while also find a way to override the `edx-platform` code from our tooling to ensure that `commerce-coordinator` functionality remains intact.
+
+Decision
+********
+
+We have decided to use `Django App Plugins`_ from `edx_django_utils`_ to override the `commerce-coordinator` related code in `edx-platform`. These plugins provide a way to override the application code without modifying the original codebase.
+Specifically we will be using the `pluggable_overrides`_ which were designed to override any method to point to an alternate implementation.
+As a result of this we will be able to pull out the `commerce-coordinator` related code from `edx-platform` and still be able to use the functionality provided by `commerce-coordinator`.
+
+Separately we have decided to create a new pluggable application that will house all the `commerce-coordinator` related code that will be used to override the `edx-platform` code. This new pluggable application will be installed with `EDXAPP_PRIVATE_REQUIREMENTS`_ from `edx-internal`_.
+
+.. _Django App Plugins: https://github.com/openedx/edx-django-utils/tree/master/edx_django_utils/plugins#django-app-plugins
+.. _edx_django_utils: https://github.com/openedx/edx-django-utils
+.. _pluggable_overrides: https://github.com/openedx/edx-django-utils/blob/master/edx_django_utils/plugins/pluggable_override.py
+.. _EDXAPP_PRIVATE_REQUIREMENTS: https://github.com/edx/edx-internal/blob/master/ansible/vars/edx.yml#L38
+.. _edx-internal: https://github.com/edx/edx-internal/
+
+Rejected Alternatives
+*********************
+
+A lengthy R&D was undertaken to look at several options for pulling out the commerce coordinator related code from `edx-platform`.
+
+Alternatives that were investigated and rejected:
+
+- Using EduNext's Ecommerce extension
+    - Rejected due to:
+        - The extension solely deals with adding more payment gateways to the ecommerce ecosystem.
+        - The extension does not provide a way to override the existing code blocks in `edx-platform`.
+        - The extension is not actively maintained.
+- Generic Flag names in edx-platform
+    - Rejected due to:
+        - This approach is not scalable.
+        - This approach will not provide a way to override the existing code blocks in `edx-platform`.