Mattermost module

[Tampa]

After using the module for a few days, weirdly no prod system wanted it yet all still stuck on Slack apparently, I do have some things that I noticed were a bit odd about it and that may improve the quality of life aspect of it, which in turn may help more folks move to it.

On mobile devices space is at a premium so any space that can be saved, by for example moving the Acknowledge button or redefining it as "Click to acknowledge" directly would reduce the space used.

The documentation for the module should mention that it is also required to add the notification rule to the contact set so the notifications are sent in the first place.

A test button would be nice to see if the notifications can be sent and the acknowledgements are also being read properly as currently the only way to test is to manually run the module through cake, which lacks the documentation on what to put into the parameters to get a proper notification display instead of an error.

Mattermost may run inside networks with only static VPN connections outside to receive data from remote systems as such it may run on different ports, this seems to be an issue with acknowledgements not being received by openitcockpit.