Extract method to get valid answers to a question

This way we remove duplication and we avoid a multi-line block in a
validation rule, which made the code hard to read.

app/models/poll/answer.rb

@@ -9,9 +9,7 @@ class Poll::Answer < ApplicationRecord
   validates :author, presence: true
   validates :answer, presence: true
 
-  validates :answer, inclusion: { in: ->(a) { a.question.question_answers
+  validates :answer, inclusion: { in: ->(a) { a.question.possible_answers }},
-                                                        .joins(:translations)
-                                                        .pluck("poll_question_answer_translations.title") }},
                      unless: ->(a) { a.question.blank? }
 
   scope :by_author, ->(author_id) { where(author_id: author_id) }

app/models/poll/partial_result.rb

@@ -10,10 +10,7 @@ class Poll::PartialResult < ApplicationRecord
   validates :question, presence: true
   validates :author, presence: true
   validates :answer, presence: true
-  validates :answer, inclusion: { in: ->(a) { a.question.question_answers
+  validates :answer, inclusion: { in: -> (a) { a.question.possible_answers }},
-                                                        .visibles
-                                                        .joins(:translations)
-                                                        .pluck("poll_question_answer_translations.title") }},
                      unless: ->(a) { a.question.blank? }
   validates :origin, inclusion: { in: VALID_ORIGINS }
 

app/models/poll/question.rb

@@ -87,4 +87,8 @@ class Poll::Question < ApplicationRecord
   def is_positive_negative?
     votation_type.present? && enum_type == "positive_negative_open"
   end
+
+  def possible_answers
+    question_answers.visibles.joins(:translations).pluck("poll_question_answer_translations.title")
+  end
 end