Add specific rate limits for posting and following (#13172)

app/controllers/api/base_controller.rb

@@ -44,6 +44,10 @@ class Api::BaseController < ApplicationController
     render json: { error: 'There was a temporary problem serving your request, please try again' }, status: 503
   end
 
+  rescue_from Mastodon::RateLimitExceededError do
+    render json: { error: I18n.t('errors.429') }, status: 429
+  end
+
   rescue_from ActionController::ParameterMissing do |e|
     render json: { error: e.to_s }, status: 400
   end