add slack notifications for wiki pages
## What does this MR do?
Lets the Slack service be configured to send notifications when wiki pages are created or edited.
## Are there points in the code the reviewer needs to double check?
I'm just starting to get familiar with the Gitlab codebase and I was unsure on how to get the wiki page url to pass it to the slack message, on whether or not I needed to refactor the create/update methods for wiki pages from the controller to a service (but seemed necessary to test it better), and if I needed to add a column to the web hooks table or if the services table would have been enough. Please let me know if I should change anything and I will improve the MR, thanks for checking :)
## Why was this MR needed?
Related to #563 and fixes#4233.
See merge request !2998
Safari 9.0 does not yet honor the HTML5 `origin-when-cross-origin` mode,
and it's possible load balancers/proxies strip the HTTP_REFERER from
the request header. In these cases, default to some default path.
Closes#3122
Closes https://github.com/gitlabhq/gitlabhq/issues/9731
Supports four different event types all bundled under the "note" event type:
- comments on a commit
- comments on an issue
- comments on a merge request
- comments on a code snippet
1) Adds a DB migration for all services to toggle on push, issue, and merge events.
2) Upon an issue or merge request event, fire service hooks.
3) Slack service supports custom messages for each of these events. Other services
not supported at the moment.
4) Label merge request hooks with their corresponding actions.
Irker is a gateway which sends IRC messages on git updates. This new
service provides an interface to this gateway, integrated in Gitlab, for
each updates.
As per the guidelines, this commit adds the new feature in the
CHANGELOG, tests and documentation.
See http://www.catb.org/esr/irker/
HipChat allows users to run their own private servers and to be able to
support those we must connect to the correct URL when using one of these
custom servers.