Include all the settings in the settings API

I would like to use the API to manage the settings of GitLab.com, but after performing a get I find the following (I'm removing most values)

{
    "after_sign_out_path": "",
    "after_sign_up_text": "",
    "container_registry_token_expire_delay": ,
    "created_at": "whenever",
    "default_artifacts_expire_in": "",
    "default_branch_protection": ,
    "default_group_visibility": "",
    "default_project_visibility": "",
    "default_projects_limit": ,
    "default_snippet_visibility": "",
    "domain_blacklist": [],
    "domain_blacklist_enabled": ,
    "domain_whitelist": [],
    "gravatar_enabled": ,
    "home_page_url": "https://about.gitlab.com/",
    "id": ,
    "koding_enabled": ,
    "koding_url": "",
    "max_attachment_size": ,
    "plantuml_enabled": ,
    "plantuml_url": "",
    "polling_interval_multiplier": ,
    "repository_storages": [
        "nfs-file09",
        "nfs-file10",
        "nfs-file11",
        "nfs-file12"
    ],
    "restricted_visibility_levels": [],
    "session_expire_delay": ,
    "sign_in_text": "",
    "signin_enabled": true,
    "signup_enabled": true,
    "terminal_max_session_time": ,
    "updated_at": "",
    "user_oauth_applications": ?
}

Comparing this list to what we have in EE, I can't help but feel that we forgot to add a bunch of things to the API

https://gitlab.com/gitlab-org/gitlab-ee/blob/master/app/controllers/admin/application_settings_controller.rb#L82-186

Additionally, it feels like repository_storages is showing the wrong thing and it's only showing the shards that are taking writes, but not all of them, which means that we are returning a partial result.

I would like this situation to be fixed, and the settings API to be feature complete with what we can configure through the web page.

cc/ @mydigitalself