Export time tracking data at the issue level

Description

We know how much time has been spent in total on an issue/MR, as well as the estimates. But we don't provide a way to easily know the evolution of time spent for this issue over time.

Description

• Add an export button on the issue/MR
• Name of the file is the issue number followed by name of the issue, with _ in place of spaces, such as 2183_export_time_tracking_data.csv
• Export the time tracking data as a csv in the following format

time spent in seconds, user #, username, full name, timestamp
3245332, 313, djaiss, Regis Freyd, 2016-10-10 12:21:54

mentioned in issue #1271 (closed)

changed title from Export time tracking data on a single issue/MR to Export time tracking data at the issue level

Closing in favour of the following issue with an ongoing ~"Community Contribution":

• https://gitlab.com/gitlab-org/gitlab-ee/issues/3803

marked this issue as a duplicate of #3803

closed

added Enterprise Edition label

changed the description

added Category:Team Planning label