added 2 settings to provide custom functions for processing data (#27)

- instead of having X forks for custom code, 2 entrypoints can be used to
  provide some possibility to change data in projects

Co-authored-by: Fabian Braun <[email protected]>

Author: wfehr

README.md

@@ -78,6 +78,15 @@ If you have a custom user model, you should designate a "migration user" by spec
 CMS_MIGRATION_USER_ID = <user id>
 ```
 
+If you want to adjust data to get the migration running in your project, there are 2 function-points available:
+
+```
+CMS_MIGRATION_PROCESS_MIGRATION_PREPARATION = "mymodule.myfunction2"
+CMS_MIGRATION_PROCESS_PAGE_REFERENCES = "mymodule.myfunction"
+```
+
+The latter function is supplied with parameters `page` and `replacement_page`.
+
 ## Running
 Simply run the following command to run the data migration.
 **Note:** This command calls the django migrate command, this is because it has to run commands that save information that would have been lost by running the cms migrations directly.

djangocms_4_migration/management/commands/migration_cleanup.py

@@ -123,6 +123,14 @@ def _fix_page_references(page):
                 **{rel.field.name: replacement_page}
             )
 
+    custom_function = getattr(settings, "CMS_MIGRATION_PROCESS_PAGE_REFERENCES", None)
+    if custom_function:
+        module, function = custom_function.rsplit(".", 1)
+        getattr(
+            __import__(module, fromlist=[""]),
+            function,
+        )(page, replacement_page)
+
 
 def _delete_page(page):
     try:

djangocms_4_migration/management/commands/migration_preparation.py

@@ -1,5 +1,6 @@
 import logging
 
+from django.conf import settings
 from django.core.management.base import BaseCommand
 from django.db import connection
 
@@ -19,3 +20,11 @@ def handle(self, *args, **options):
                 cursor.execute("DROP table djangocms_history_placeholderoperation;")
         except:
             logger.info("djangocms_history already removed")
+
+        custom_function = getattr(settings, "CMS_MIGRATION_PROCESS_MIGRATION_PREPARATION", None)
+        if custom_function:
+            module, function = custom_function.rsplit(".", 1)
+            getattr(
+                __import__(module, fromlist=[""]),
+                function,
+            )()