fix: no comportarse como un array

app/models/metadata_has_one.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-class MetadataHasOne < MetadataHasMany
+class MetadataHasOne < MetadataBelongsTo
   def had_one
     return default_value if value_was.blank?
 
@@ -13,11 +13,18 @@ class MetadataHasOne < MetadataHasMany
     posts.find(uuid: value)
   end
 
-  def had_many; end
-  def has_many; end
+  def belonged_to; end
+  def belongs_to; end
 
   def save
-    super
+    # XXX: DRY
+    if !changed?
+      self[:value] = document_value
+
+      return true
+    end
+
+    self[:value] = sanitize value
 
     return true unless changed?
     return true unless inverse?
@@ -31,4 +38,8 @@ class MetadataHasOne < MetadataHasMany
   def related_methods
     @related_methods ||= %i[has_one had_one].freeze
   end
+
+  def indexable_values
+    has_one&.title&.value
+  end
 end