comment creation - participant service

Create a service for the participant comment creation.

This is a child of #5 (closed)

changed time estimate to 2h

changed the description

added ToDo label

assigned to @hdrs71

added WIP and removed ToDo labels

mentioned in merge request !46 (merged)

added 1h of time spent at 2018-03-08

added ~1064 and removed WIP labels

added ready for review and removed ~1064 labels

closed via commit 67d6de46

closed via merge request !46 (merged)

mentioned in commit 67d6de46