allow DesignerEnrollments in the API; fixes #CNVS-2147

the API was created without the ability to enroll Designers.
we think this was an oversight.

test plan:
 - enroll a designer via the API
 - enroll a custom role based on designer via the API

Change-Id: Idee15513dd001500a710ecf73eed56f92cac47c4
Reviewed-on: https://gerrit.instructure.com/16029
Reviewed-by: Bracken Mosbacker <bracken@instructure.com>
QA-Review: Adam Phillipps <adam@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>

app/controllers/enrollments_api_controller.rb

@@ -31,7 +31,6 @@ class EnrollmentsApiController < ApplicationController
     :concluded_course   => 'Can\'t add an enrollment to a concluded course.'
 
   }
-  @@valid_types = %w{StudentEnrollment TeacherEnrollment TaEnrollment ObserverEnrollment}
 
   include Api::V1::User
   # @API List enrollments
@@ -165,7 +164,7 @@ class EnrollmentsApiController < ApplicationController
   # Create a new user enrollment for a course or section.
   #
   # @argument enrollment[user_id] [String] The ID of the user to be enrolled in the course.
-  # @argument enrollment[type] [String] [StudentEnrollment|TeacherEnrollment|TaEnrollment|ObserverEnrollment] Enroll the user as a student, teacher, TA, or observer. If no value is given, 'StudentEnrollment' will be used.
+  # @argument enrollment[type] [String] [StudentEnrollment|TeacherEnrollment|TaEnrollment|ObserverEnrollment|DesignerEnrollment] Enroll the user as a student, teacher, TA, observer, or designer. If no value is given, the type will be inferred by enrollment[role] if supplied, otherwise 'StudentEnrollment' will be used.
   # @argument enrollment[role] [String] [Optional] Assigns a custom course-level role to the user.
   # @argument enrollment[enrollment_state] [String] [Optional, active|invited] [String] If set to 'active,' student will be immediately enrolled in the course. Otherwise they will be required to accept a course invitation. Default is 'invited.'
   # @argument enrollment[course_section_id] [Integer] [Optional] The ID of the course section to enroll the student in. If the section-specific URL is used, this argument is redundant and will be ignored
@@ -198,7 +197,7 @@ class EnrollmentsApiController < ApplicationController
       end
 
       if type.present?
-        errors << @@errors[:bad_type] unless @@valid_types.include?(type)
+        errors << @@errors[:bad_type] unless Enrollment.valid_type?(type)
       else
         type = 'StudentEnrollment'
       end

app/models/enrollment.rb

@@ -215,6 +215,10 @@ class Enrollment < ActiveRecord::Base
     self.role_name || Enrollment.sis_type(self.type)
   end
 
+  def self.valid_type?(type)
+    SIS_TYPES.has_key?(type)
+  end
+
   TYPES_WITH_INDEFINITE_ARTICLE = {
     'TeacherEnrollment' => t('#enrollment.roles.teacher_with_indefinite_article', "A Teacher"),
     'TaEnrollment' => t('#enrollment.roles.ta_with_indefinite_article', "A TA"),

spec/apis/v1/enrollments_api_spec.rb

@@ -160,6 +160,12 @@ describe EnrollmentsApiController, :type => :integration do
         JSON.parse(response.body)['message'].should eql 'Invalid type'
       end
 
+      it "should enroll a designer" do
+        json = api_call :post, @path, @path_options, { :enrollment => { :user_id => @unenrolled_user.id, :type => 'DesignerEnrollment' } }
+        json['type'].should eql 'DesignerEnrollment'
+        @unenrolled_user.enrollments.find(json['id']).should be_an_instance_of(DesignerEnrollment)
+      end
+
       it "should return an error if no user_id is given" do
         raw_api_call :post, @path, @path_options, { :enrollment => { :type => 'StudentEnrollment' } }
         response.code.should eql '403'