If a field has been hidden or is not in a context for an issue, it will be displayed on the confirmation page for move or convert issue, if the system thinks it has a value.

The system will think it has a value if it is calculated field or if it has a value in the database. (i.e. the field used to be in context or not hidden, was given a value and then removed from context or hidden).

When retrieving removed fields, we must find the intersection of all hidden fields for the target context and all displayed fields in the current context.

This should be done in DefaultIssueConversionService.getRemovedFields()