Fix being able to vote on your own polls (mastodon#25015)

(cherry picked from commit cca464b)

app/validators/vote_validator.rb

@@ -3,8 +3,8 @@
 class VoteValidator < ActiveModel::Validator
   def validate(vote)
     vote.errors.add(:base, I18n.t('polls.errors.expired')) if vote.poll.expired?
-
     vote.errors.add(:base, I18n.t('polls.errors.invalid_choice')) if invalid_choice?(vote)
+    vote.errors.add(:base, I18n.t('polls.errors.self_vote')) if self_vote?(vote)
 
     if vote.poll.multiple? && vote.poll.votes.where(account: vote.account, choice: vote.choice).exists?
       vote.errors.add(:base, I18n.t('polls.errors.already_voted'))
@@ -18,4 +18,8 @@ def validate(vote)
   def invalid_choice?(vote)
     vote.choice.negative? || vote.choice >= vote.poll.options.size
   end
+
+  def self_vote?(vote)
+    vote.account_id == vote.poll.account_id
+  end
 end

config/locales/en.yml

@@ -1387,6 +1387,7 @@ en:
       expired: The poll has already ended
       invalid_choice: The chosen vote option does not exist
       over_character_limit: cannot be longer than %{max} characters each
+      self_vote: You cannot vote in your own polls
       too_few_options: must have more than one item
       too_many_options: can't contain more than %{max} items
   preferences: