Adds `# frozen_string_literal: true` to spec/models ruby files

Filter web hooks by branch

See merge request gitlab-org/gitlab-ce!19513

This whitelists all existing places where we use "destroy_all".

Allow specificying a branch filter for a project hook and only trigger
a project hook if either the branch filter is blank or the branch matches.
Only supported for push_events for now.

For reasons unknown, the logs of a web hook were paginated in memory.
This would result in the "Edit" page of a web hook timing out once it
has more than a few thousand log entries.

This commit makes the following changes:

1. We use LIMIT/OFFSET to paginate the data, instead of doing this in
   memory.

2. We limit the logs to the last two days, just like the documentation
   says (instead of retrieving everything).

3. We change the indexes on "web_hook_logs" so the query to get the data
   can perform a backwards index scan, without the need for a Filter.

These changes combined ensure that Projects::HooksController#edit no
longer times out.

System hooks for Merge Requests

See merge request gitlab-org/gitlab-ce!14387

Don't allow line breaks on HTTP headers

See merge request gitlab/gitlabhq!2277

(cherry picked from commit 7fc0a6fc096768a5604d6dd24d7d952e53300c82)

073b8f9c Don't allow line breaks on HTTP headers