[11.9] Revert "Remove HipChat integration from GitLab"

See merge request gitlab-org/gitlab-ce!27257

Partially addresses #47424.

[10.6] Prevent notes on confidential issues from being sent to chat

See merge request gitlab/gitlabhq!2366
# Conflicts:
#	app/helpers/services_helper.rb

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

Adds a rubocop rule (with autocorrect) to ensure line break after guard clauses.

An upcoming update to rubocop-gitlab-security added additional
violations.

Use the EnforcedStyleForMultiline: no_comma option.

Signed-off-by: Rémy Coutable <remy@rymai.me>

The `class` and `data-*` attributes are meaningless in HipChat, and it
would probably be better to limit the tags, too. For example, we could
avoid block-level elements in `render_line`.

"pipeline: :single_line" leaves the protocol/host part out of the URLs
and caches them that way. To avoid giving those out to HipChat, markdown
is always rendered with "pipeline: :email" first.

There must be a better way to do this, but I can't see how to avoid the
link caching.

Using "pipeline: :email" gets "only_path: false" into the context to
produce full URLs instead of /namespace/project/...

The `class` and `data-*` attributes are meaningless in HipChat, and it
would probably be better to limit the tags, too. For example, we could
avoid block-level elements in `render_line`.

"pipeline: :single_line" leaves the protocol/host part out of the URLs
and caches them that way. To avoid giving those out to HipChat, markdown
is always rendered with "pipeline: :email" first.

There must be a better way to do this, but I can't see how to avoid the
link caching.

Using "pipeline: :email" gets "only_path: false" into the context to
produce full URLs instead of /namespace/project/...

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

This reverts commit 3e991230.