Openproject notification

### Discussed in https://github.com/girish17/op-mattermost/discussions/36

<div type='discussions-op-text'>

<sup>Originally posted by **wolfjudge** July 20, 2022</sup>
Hello,
Just wanted to check if there is a possibility to have this integrated in a way that openproject send notifications to specific mattermost channel?
Tnx in advance 
Judge</div>