### Steps to reproduce

1. Have two accounts with the same email address in Jira

2. Login to OP as a user with permissions to migrate from Jira

3. Start a migration run of a project/issue where both accounts are used


### What is the buggy behavior?

* The run is stopped with an error message Begin of the insertion

<br>

End of the insertion Begin of the deletion
End of the deletion `Import::JiraOpenProjectReference with jira_entity_class Import::JiraUser and jira_entity_id 1486 not found!`


### What is the expected behavior?

1. The import run continues without errors

2. To satisfy OpenProject requirement of unique emails, the duplicated email is amended via the sub addressing mechanism [https://en.wikipedia.org/wiki/Email\_address#Sub-addressing](https://en.wikipedia.org/wiki/Email_address#Sub-addressing) with the accounts’ Jira key
e.g. `someone@example.com` ⇒ Begin of the insertion[`someone+JIRA0001@example.com`](mailto:someone+JIRA0001@example.com)
&nbsp;  `someone+abc@example.com` ⇒ [`someone+abc+JIRA0001@example.com`](mailto:someone+JIRA0001@example.com)End of the insertion Begin of the deletion `someone+JIRA0001@example.com`End of the deletion


### Screenshots and other files

<img class="op-uc-image op-uc-image_inline" src="/api/v3/attachments/922403/content">

### Environment information

**OpenProject installation type**

* All


**OpenProject version**

* All since Jira migration beta release


**Browser**

* All


**Operating System**

* All


**Language**

* All