move methods from analyze helper to background presenter

app/models/analysis_graph/students_and_teachers.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module AnalysisGraph
   class StudentsAndTeachers
     def to_s
@@ -7,5 +9,9 @@ module AnalysisGraph
     def value
       'students-and-teachers'
     end
+
+    def columns
+      [StudentGroupedBarColumnPresenter, TeacherGroupedBarColumnPresenter, GroupedBarColumnPresenter]
+    end
   end
 end

app/models/analysis_graph/students_by_group.rb

@@ -7,5 +7,9 @@ module AnalysisGraph
     def value
       'students-by-group'
     end
+
+    def columns
+      [StudentGroupedBarColumnPresenter]
+    end
   end
 end