Use image proxy to mitigate stealing ip addresses

Closes #2812

See merge request gitlab/gitlabhq!2926

Filter out old system notes for epics in notes api endpoint response

See merge request gitlab/gitlabhq!3224

Require a captcha after unique failed logins from the same IP

See merge request gitlab/gitlabhq!3270

Standardize use of `content` parameter in snippets API

Closes #66673

See merge request gitlab-org/gitlab-ce!32296

There was some confusion over whether `code` or `content` is the right
parameter for snippets. Internally, the database stores
`content`. However:

1. Project snippets use `code`. `code` gets remapped in `content` in
`lib/api/project_snippets.rb`.

2. Personal snippets use `content`.

To unify these APIs, allow an alias of `content` to work for project
snippets.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/66673

Instead of sending varied data to Gitaly, and making Gitaly construct
various messages, build the messages first and have Gitaly print
either basic messages or alert messages, in the order they come.

Depends on https://gitlab.com/gitlab-org/gitaly/merge_requests/1410

A new param with_security_reports was added to
GET /groups/:id/projects API and the code to
support this logic in GroupProjectsFinder and
Project model. Also, a DB index was added to
ci_job_artifacts table to speed up the search
of security reports artifacts for projects

(cherry picked from commit 897a9d308db46b620b738b98f2b0e5630ac7d2dd)