Issue Summary

All fields (custom or standard) will always be migrated (if supported) or come up in the pre-migration report (if unsupported), even though it is not referenced by a selected project.

Steps to Reproduce

Example 1: Supported standard field

1. Change a standard field from Global to being used by 0 projects
2. Ensure that the field is used in 0 screens
3. Migrate a project
4. Observe that this standard field is still migrated even though it was not referenced in the project data

Example 2: Supported custom field

1. Ensure there is a supported custom field type configured in the Jira Server instance
2. Migrate a project which does not have this custom field referenced in the data
3. Observe that the custom field is still migrated even though it was not referenced in the project data

Example 3: Unsupported custom field

1. Ensure there is an unsupported custom field type configured in the Jira Server instance
2. Migrate a project which does not have this custom field referenced in the data
3. Observe that the unsupported custom fields is reported in the 'Pre-migration report' as it is considered part of the data set (Note: the report is still in development)

Expected Results

For selected projects:

• Only migrate referenced standard fields. 
• Only migrate referenced custom fields.
  • Only report on referenced unsupported custom fields

Actual Results

All custom and standard fields are migrated every time a migration is run. This means that fields not required by the selected projects are migrated, resulting in longer migration runs, high risk of project migration failure and a higher burden on Cloud performance.

If the field is supported - it can create noise in the destination instance by migrating fields that are not used by any project. 
If the field is unsupported - it can create noise in the pre and post migration ‘Requires Attention' report by reporting to the customer that the field config won’t be migrated and that they should either fix/clean-up the issue unnecessarily. 

Workaround

Delete the custom fields that are not required post-migration.