Users with duplicate emails are merged when using CCMA

Issue Summary

When using CCMA - using option Only users related to the selected spaces, user accounts with duplicate email addresses are merged in the cloud site.

Steps to Reproduce

Tested with latest CCMA version 3.20

1. Created user 'test8' with email 'sms2@atlassian.com', followed by user *'test7'*using the same email address.
2. Created a space named 7-space using test7.
3. And created a new page test7space-page with user test7 and edited the page and commented on it using first user test8.
4. Created another page with user test8.
5.  Migrated the space to the cloud site using option Only users related to the selected spaces, the migration completed successfully.

Expected Results

• Either the migration should fail or not be allowed to be run until all duplicates and invalids are fixed OR,
• Customer should be provided an option so that he can choose which user the content should get merged to.

Actual Results

• We noticed that test8 user got migrated to the cloud site (because it was created first on the server than test7)
• And all the content of test7 user got merged with test8 user.

Workaround

Currently, there is no known workaround for this behavior.