Initial v2 API Implementation & Doorkeeper OAuth Integration

[aaronskiba]

Overview:

This PR introduces the initial implementation of DMP Assistant's v2 API, with OAuth 2.0 authentication powered by the Doorkeeper gem. This is a foundation for further v2 API enhancements and ensures secure, standards-based authentication for future integrations.

Key Features:

• Integrates Doorkeeper gem for OAuth 2.0 and v2 access token management.
• Implements initial v2 API endpoints:
  • GET /api/v2/plans
  • GET /api/v2/plans/:id
  • GET /api/v2/templates
  • GET /api/v2/me
  • GET /api/v2/heartbeat
    • NOTE: The responses for GET /plans and GET /plans/:id calls serialize plan data according to the RDA DMP Common Standard JSON schema.
• Adds optional “complete” flag for GET /plans and GET /plans/:id (Add complete plan flag to V2 API DMPRoadmap/roadmap#3595).
• Enables internal v2 API access token generation for users (Add Internal v2 API Access Token Generation for Users #1279).
• Adds test coverage Add v2 API Test Coverage and Address Uncovered Bugs DMPRoadmap/roadmap#3589

[aaronskiba]

@minimal is referenced here, but not assigned anywhere. I can see the following usage of it in Api:V1:

# app/controllers/api/v1/plans_controller.rb
def index
  plans = Api::V1::PlansPolicy::Scope.new(client, Plan).resolve
  if plans.present? && plans.any?
    @items = paginate_response(results: plans)
    @minimal = true
    render 'api/v1/plans/index', status: :ok

And then a unless @minimal is performed in app/views/api/v1/plans/_show.json.jbuilder.

[aaronskiba]

I know that this code is largely based off of https://github.com/CDLUC3/dmptool. They have the following in Api::V2::PlansController#index:

      def index
        # Scope here is not the Doorkeeper scope, its just to refine the results
        @scope = 'mine'
        @scope = params[:scope].to_s.downcase if %w[mine public both].include?(params[:scope].to_s.downcase)

        # See the Policy for details on what Plans are returned to the Caller based on the AccessToken
        plans = Api::V2::PlansPolicy::Scope.new(@client, @resource_owner, @scope).resolve

        if plans.present? && plans.any?
          plans = plans.sort { |a, b| b.updated_at <=> a.updated_at }
          @items = paginate_response(results: plans)
          @minimal = true
          render 'api/v2/plans/index', status: :ok
        else
          render_error(errors: _('No Plans found'), status: :not_found)
        end
      end

[momo3404]

Great work on this!