adds test to check whether or not an email is sent to label subscribers after creating a new issue through the api

- Refactored SpamCheckService into SpamService

- Removed unnecessary column from `SpamLog`
- Moved creation of SpamLogs out of its own service and into SpamCheckService
- Simplified code in SpamCheckService.
- Moved move spam related code into Spammable concern

- Merged `AkismetSubmittable` into `Spammable`
- Clean up `SpamCheckService`
- Added tests for `Spammable`
- Added submit (ham or spam) options to `AkismetHelper`

Refactor spam validation to a concern that can be easily reused and improve legibility in `SpamCheckService`

rely only on IssuesFinder
docs and changelog

This only supports Issues and MergeRequests right now because of the
consistency of the routes those models provide.

This was not a clear cut n+1 query, given that if you're directly subscribed to all issues
that the API is returning you never really need to check for the notes. However, if you're
subscribed to _all_ of them, then for each issuable you need to go once to `notes`, and
once to `users` (for the authors). By preemtively loading notes and authors, at worst you have
1 extra query, and at best you saved 2n extra queries. We also took advantage of this preloading
of notes when counting user notes.

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

Closes #15638

Previously all remote IPs appeared at 127.0.0.1, which made Akismet
not very useful. Using the ActionDispatch Remote IP (http://api.rubyonrails.org/classes/ActionDispatch/RemoteIp.html)
should provide more reliable results.

Closes #16629

Currently any spam detected by Akismet by non-members via API will be logged
in a separate table in the admin page.

Closes #5612

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

write_ was renamed to create_
modify_  was renamed to update_

So now in update action we have next code

def create
  can?(current_user, :create_issue, @issue)
end

def update
  can?(current_user, :update_issue, @issue)
end
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>