Default custom field values can be stripped when issues are created via email

com.atlassian.jira.service.util.handler.DefaultMessageHandlerContext is used as a com.atlassian.jira.service.util.handler.MessageHandlerContext to truncate content that exceeds length limits when creating an issue from an email message.

The createIssue method obtains a MutableIssue reference by using IssueFactory.cloneIssue which is a shallow copy. The impact is all default custom field values are missing from the issue whenever the description or environment fields are truncated.