Migrate using All Data at Once causes attachment links to be broken

Issue Summary

Migrating server instance using all data at once will not fail but will result into attachment links and Avatar links to be broken. 

Steps to Reproduce

1. Using JCMA 1.7.8 
2. Choose migrate All data at once. 
3. Finish the migration
4. Go to cloud site
5. Issues containing avatars or Attachments will have broken links

Expected Results

All links should not be broken.

Actual Results

Workaround

Workaround #1 - Recommended

Issue has been fixed in JCMA Version 1.8.0

Workaround #2 - Incase you can't upgrade to JCMA Version 1.8.0

To fix the attachment linking issue for customers who have already made a migration using 1.7.8 version, customers can fix the attachment linking follow the instructions below:

1. Enable the following dark feature flags
com.atlassian.jira.migration.media-linking-legacy.feature

com.atlassian.jira.migration.enable.site-import-enricher{}

2. Create a new Attachment Only migration

3. Choose "Attachment linking" and tick "Force re-linking"

4. Tick all projects

5. And run the migration