Validate length of user's name attribute

This attribute is a text column, so it could be very long even in a
MySQL database. Limit it to a generous length.

publify_core/app/models/user.rb

@@ -22,6 +22,7 @@ class User < ApplicationRecord
   validates :email, :login, presence: true
   validates :login, length: { in: 3..40 }
   validates_default_string_length :email, :text_filter_name
+  validates :name, length: { maximum: 2048 }
 
   belongs_to :resource, optional: true
   has_many :notifications, foreign_key: "notify_user_id"

publify_core/spec/models/user_spec.rb

@@ -49,6 +49,10 @@
       expect(user).to validate_length_of(:email).is_at_most(255)
     end
 
+    it "requires name to not be too long" do
+      expect(user).to validate_length_of(:name).is_at_most(2048)
+    end
+
     it "requires first name to not be too long" do
       expect(user).to validate_length_of(:firstname).is_at_most(256)
     end