Update config files related to omniauth

Author: constantine-nikolaou

app/views/devise/shared/_omniauthable.html.erb

@@ -1,6 +1,6 @@
 <%- if devise_mapping.omniauthable? %>
   <%- resource_class.omniauth_providers.each do |provider| %>
-    <%= link_to(user_slack_omniauth_authorize_path) do %>
+    <%= link_to(user_slack_omniauth_authorize_path, method: :post) do %>
       <!-- "Sign in with #{OmniAuth::Utils.camelize(provider)}" -->
       <%= image_tag('https://platform.slack-edge.com/img/sign_in_with_slack.png',
                     alt: 'Sign in with Slack',

config/initializers/omniauth.rb

@@ -1,3 +1,6 @@
+# Configure OmniAuth to only allow requests from :post and :get
+OmniAuth.config.allowed_request_methods = [:post, :get]
+
 if !AppSettings.slack_app_client_id.blank? && !AppSettings.slack_app_client_secret.blank?
   Rails.application.config.middleware.use(OmniAuth::Builder) do
     provider :slack,