Add ProgrammingGroup & ProgrammingGroupMembership

* User can create programming group with other users for exercise
* Submission is shared in a group
* Also adjust specs

app/policies/application_policy.rb

@@ -49,6 +49,13 @@ class ApplicationPolicy
   end
   private :teacher_in_study_group?
 
+  def author_in_programming_group?
+    return false unless @record.contributor.programming_group?
+
+    @record.contributor.users.include?(@user)
+  end
+  private :author_in_programming_group?
+
   def initialize(user, record)
     @user = user
     @record = record

app/policies/programming_group_policy.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class ProgrammingGroupPolicy < ApplicationPolicy
+  def new?
+    everyone
+  end
+
+  def create?
+    everyone
+  end
+end

app/policies/submission_policy.rb

@@ -9,7 +9,7 @@ class SubmissionPolicy < ApplicationPolicy
   # download_submission_file? is used in the live_streams_controller.rb
   %i[download? download_file? download_submission_file? run? score? show? statistics? stop? test?
      insights?].each do |action|
-    define_method(action) { admin? || author? }
+    define_method(action) { admin? || author? || author_in_programming_group? }
   end
 
   def render_file?