Store and retrieve avatars in/from LDAP exclusively

No need to keep them in two places at the same time. We can fetch them
from LDAP whenever we want to do something with them.

app/models/user.rb

@@ -2,19 +2,10 @@ class User < ApplicationRecord
   include EmailValidatable
 
   attr_accessor :display_name
+  attr_accessor :avatar_new
 
   serialize :preferences, UserPreferences
 
-  #
-  # File attachments
-  #
-
-  has_one_attached :avatar do |attachable|
-    attachable.variant :small,  resize_to_fill: [64, 64],   convert: :jpeg
-    attachable.variant :medium, resize_to_fill: [256, 256], convert: :jpeg
-    attachable.variant :large,  resize_to_fill: [512, 512], convert: :jpeg
-  end
-
   #
   # Relations
   #
@@ -167,9 +158,8 @@ class User < ApplicationRecord
     @display_name ||= ldap_entry[:display_name]
   end
 
-
-  def avatar_base64(variant: :large)
-    Base64.strict_encode64 avatar.variant(variant).processed.download
+  def avatar
+    @avatar_base64 ||= LdapManager::FetchAvatar.call(cn: cn, ou: ou)
   end
 
   def services_enabled
@@ -202,14 +192,14 @@ class User < ApplicationRecord
     end
 
     def acceptable_avatar
-      return unless avatar.attached?
+      return unless avatar_new.present?
 
-      if avatar.blob.byte_size > 1.megabyte
+      if avatar_new.size > 1.megabyte
         errors.add(:avatar, "file size is too large")
       end
 
       acceptable_types = ["image/jpeg", "image/png"]
-      unless acceptable_types.include?(avatar.content_type)
+      unless acceptable_types.include?(avatar_new.content_type)
         errors.add(:avatar, "must be a JPEG or PNG file")
       end
     end