This adds a `markdown_field` to our types.

Using this helper will render a model's markdown field using the
existing `MarkupHelper` with the context of the GraphQL query
available to the helper.

Having the context available to the helper is needed for redacting
links to resources that the current user is not allowed to see.

Because rendering the HTML can cause queries, the complexity of a
these fields is raised by 5 above the default.

The markdown field helper can be used as follows:

      ```
      markdown_field :note_html, null: false
      ```

This would generate a field that will render the markdown field `note`
of the model. This could be overridden by adding the `method:`
argument. Passing a symbol for the method name:

      ```
      markdown_field :body_html, null: false, method: :note
      ```

It will have this description by default:

> The GitLab Flavored Markdown rendering of `note`

This could be overridden by passing a `description:` argument.

The type of a `markdown_field` is always `GraphQL::STRING_TYPE`.

We can query namespaces, and nested projects.

Projects now exposes statistics

Enables authorizations to be defined on GraphQL Types.

    module Types
      class ProjectType < BaseObject
        authorize :read_project
      end
    end

If a field has authorizations defined on it, and the return type of the
field also has authorizations defined on it. then all of the combined
permissions in the authorizations will be checked and must pass.

Connection fields are checked by "digging" to find the type class of the
"node" field in the expected location of edges->node.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/54417

And add tests

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

This suggests possibly related issues when the user types a title.

This uses GraphQL to allow the frontend to request the exact
data that is requires. We also get free caching through the Vue Apollo
plugin.

With this we can include the ability to import .graphql files in JS
and Vue files.
Also we now have the Vue test utils library to make testing
Vue components easier.

Closes #22071

This adds Keyset pagination to GraphQL lists. PoC for that is
pipelines on merge requests and projects.

When paginating a list, the base-64 encoded id of the ordering
field (in most cases the primary key) can be passed in the `before` or
`after` GraphQL argument.

This adds a reusable way to expose permissions for a user to types in
GraphQL.

This allows the user to get a single MR nested in a GraphQL project
query.

Since we need the full path and the iid anyway, this makes more sense
than having a root query that needs the full path as well.

- All definitions have been replaced by classes:
  http://graphql-ruby.org/schema/class_based_api.html
- Authorization & Presentation have been refactored to work in the
  class based system
- Loaders have been replaced by resolvers
- Times are now coersed as ISO 8601