I have a very specific question, maybe somebody knows anything.
We have a role within our company which would be the best described as a "External Consultant". We don't want to include those persons into jira because they need to be decoupled as far as possible from our internal processes to provide the best work.
Nonetheless we need to automatically communicate with them somehow when some Jira-Issues transition states.
We used to do so through Sending E-Mails through Workflow Post Functions and an E-Mail Addon.
Because E-Mails tend to lead to a big mess (when getting 5 mails for the same issue for example) we were thinking about using something like Slack / Hipchat where each Consultant has his own Channel and through JIRA Workflow Post Functions short Notifications are delivered to the specific Channels.

After some testing I found out that there is no way of sending Slack / Hipchat Notifications from a JIRA Post Function (tried a lot of addons). Now the big question: Does anybody know any different system like Slack which provides JIRA Post-Workflow Integration?
The last solution would be to use some Zapier-Integrations but this would cause the system to get very complex.