Add License Management API to the backend

What does this MR do?

It adds approval and blacklist API for software licenses; see https://gitlab.com/gitlab-org/gitlab-ee/issues/5488

Why was this MR needed?

To implement https://gitlab.com/gitlab-org/gitlab-ee/issues/5488

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• EE specific content should be in the top level /ee folder
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Refs #5488 (closed)

app/controllers/projects/managed_licenses_controller.rb

@@ -4,6 +4,8 @@ class Projects::ManagedLicensesController < Projects::ApplicationController
   before_action :managed_license, only: [:show, :edit, :update, :destroy]
   before_action :authorize_admin_build!
 
+  rescue_from ArgumentError, with: -> { respond_400 }
+
   def index
     respond_to do |format|
       format.json do
@@ -42,7 +44,7 @@ def edit
   end
 
   def update
-    @managed_license = ManagedLicenses::UpdateService.new(managed_licenses_params).execute(project: @project)
+    @managed_license = ManagedLicenses::UpdateService.new(managed_licenses_params).execute(@managed_license)
 
     if @managed_license.valid?
       respond_to do |format|
@@ -65,12 +67,21 @@ def destroy
 
   private
 
+  def respond_400
+    head :bad_request
+  end
+
   def managed_license
     @managed_license ||= @project.managed_licenses.find(params[:managed_license_id])
+
+    if @managed_license.nil? then
+      # The license was not found
+      render_404
+    end
   end
 
   def render_ok
-    render status: :ok
+    render status: :ok, nothing: true
   end
 
   def render_managed_license
@@ -86,10 +97,10 @@ def render_error(error, status=400)
   end
 
   def managed_licenses_params
-    params.permit(managed_licenses_attributes: [*managed_license_params_attributes])
+    params.require(:managed_license).permit([:id, :name, :approval_status]) #permit(managed_licenses_attributes: [*managed_license_params_attributes])
   end
 
-  def managed_license_params_attributes
-    %i[id name approval_status _destroy]
-  end
+  #def managed_license_params_attributes
+  #  %i[id name approval_status _destroy]
+  #end
 end