Resolve "comment creation api"

WIP

Informationen

• API connection implemented
• old in-memory-data removed
• comment-list feature for participant removed

#145 (closed) related -> comment-list is in the moment in usage for creator and participant, api doesnt support this feature, comment-list for participant have to be saved in local storage

Testing

• check functionality for creator comment-list

Closes #98 (closed)