Add icon_url to apps

app/views/carto/oauth_provider/_avatars.html.erb

@@ -1,6 +1,6 @@
 <div class='oauth-form__avatars'>
-  <%if (current_user && current_user.avatar) %> <!-- #TODO use variable like 'current_app' & 'current_app.avatar' -->
-    <img class='oauth-form__avatar-image' src="<%= current_user.avatar %>" alt="<%= current_user.username %>" />
+  <% if @oauth_app %>
+    <img class='oauth-form__avatar-image' src="<%= @oauth_app.icon_url %>" alt="<%= @oauth_app.name %>" />
   <% else %>
     <img class='oauth-form__avatar-image' src="<%= image_path "oauth_provider/unknown_app_avatar.svg" %>" alt="Unknown app avatar">
   <% end %>

db/migrate/20180817160934_add_avatar_url_to_oauth_apps.rb

@@ -0,0 +1,12 @@
+require 'carto/db/migration_helper'
+
+include Carto::Db::MigrationHelper
+
+migration(
+  Proc.new do
+    add_column :oauth_apps, :icon_url, :text, null: false
+  end,
+  Proc.new do
+    drop_column :oauth_apps, :icon_url
+  end
+)