Support Users Directly Uploading Profile Pictures.

* Adds a `picture` attribute to `User`.
* Preserves Gravatar as a fallback option.
* Now, you should use `user.profile_picturer` instead of `gravatar_url`
* TODO: Ensure `profile_picture` handles sizing right for uploaded images.

app/models/user.rb

@@ -23,9 +23,13 @@ class User < ApplicationRecord
   has_paper_trail on: [:create, :update], ignore: [:sign_in_count, :remember_created_at, :current_sign_in_at, :last_sign_in_at, :current_sign_in_ip, :last_sign_in_ip, :unconfirmed_email,
                                                    :avatar_content_type, :avatar_file_size, :avatar_updated_at, :updated_at, :confirmation_sent_at, :confirmation_token, :reset_password_token]
 
+  # A user may have an uploaded avatar or use gravatar.
+  # The uploaded picture takes precedence.
   include Gravtastic
   gravtastic size: 32
 
+  mount_uploader :picture, PictureUploader, mount_on: :picture
+
   before_create :setup_role
 
   after_save :touch_events
@@ -151,6 +155,14 @@ class User < ApplicationRecord
     ticket_purchases.find_by(conference_id: conference.id).present?
   end
 
+  ##
+  # Returns a user's profile picture URL.
+  # Partials should *not* directly call `gravatar_url`
+  def profile_picture(opts)
+    # TODO: Figure out how to align sizes?
+    picture.thumb.url || gravatar_url(opts)
+  end
+
   def self.for_ichain_username(username, attributes)
     user = find_by(username: username)