Redirect projects/:id to project page

Inspired by https://gitlab.com/gitlab-org/gitlab-ee/issues/8280.

When doing integrations or some sort of administrations you might know project id but not a project name. To make project discover easier I propose we add a route to redirect project ID to project page.

For example when user types https://gitlab.com/projects/13083 in the browser they will be redirected to https://gitlab.com/gitlab-org/gitlab-ce

This can be achieved by some simple code like

get 'projects/:id:' => 'projects#resolve'

def resolve
  project = Project.find(params[:id])
  
  redirect_to project
end