When a custom field is configured as the Estimation Statistic, it is no longer available to add to the Issue Detail View

Issue Summary

When a Custom Field is set to be the board's Estimation Statistic, it is no longer available to be added to the Issue Detail View

This was probably an intentional decision, since a SCRUM board displays the content of the Estimation Custom Field at the top as Estimate, however, it is actually possible for a KANBAN board to have estimation set (should not be possible), and this results in the field not being displayed.

In any case, a customer may wish to have the custom field used for estimation displayed

Steps to Reproduce

1. Create a SCRUM board and a test issue
2. Create a numeric custom field, assign to project, and give the test issue a value
3. Configure the board, visit Estimation, and use the custom field as the estimation statistic
4. Refresh the configure board page
5. Click Issue Detail View

Expected Results

• The custom field can be added to the Issue Detail View under General fields
• The field is returned via /rest/greenhopper/1.0/detailviewfield/12345/available

Actual Results

• The custom field is removed from the list of fields to add
• The field is not returned via /rest/greenhopper/1.0/detailviewfield/12345/available

For customers having this problem on KANBAN board, you can confirm this is the cause by checking the editmodel.json response in browser Network Tools. Observe the estimation statistic is configured for your problematic custom field:

},
  "estimationStatisticConfig": {
    "rapidViewId": 12345,
    "canEdit": true,
    "currentEstimationStatistic": {
      "typeId": "field",
      "fieldId": "customfield_13000",
      "id": "field_customfield_13000",
      "name": "Custom Field Name Here",
      "isValid": true,
      "isEnabled": true,
      "renderer": "number"
    }, 

Workaround

For SCRUM board:

1. Set the estimation to Story Points
2. Refresh the configuration screen
3. Add the custom field to Issue Detail View
4. Change the estimation again to the Custom Field

For KANBAN board:

1. Make a new board via REST API, replacing the variables as required:

   curl -vvv -X POST -u ADMIN_USER https://YOUR_JIRA/rest/agile/1.0/board --data '{"name":"New Board", "type":"kanban", "filterId":YOUR_FILTER_ID}' -H 'Content-Type: application/json' 

2. Visit the Project, then hover over the top left icon on the board, and select your new board
3. Reconfigure the board as per desire (EG, column mappings, subquery, etc)
4. Finally, delete the original problematic board