Resolve "Export issue time tracking information"

Merged Bohdan V. requested to merge smcgivern/gitlab-ee:1406-new-export-fields into master

What does this MR do?

Per issue added:

  • Current time estimate. Field Time Estimate
  • Current time spent. Field Time Spent
  • The format of the two fields should be in seconds

Are there points in the code the reviewer needs to double check?

  • check that logic is correct
  • check if additional documentation/changelog entry needed

Why was this MR needed?

Need to have an ability to see estimates/reports in exported file.

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?

Closes #1406 (closed)

Edited by Bohdan V.