Explicitly disable storage of REST API results (#10655)

Fixes #10652

app/controllers/api/base_controller.rb

@@ -9,6 +9,8 @@ class Api::BaseController < ApplicationController
   skip_before_action :store_current_location
   skip_before_action :check_user_permissions
 
+  before_action :set_cache_headers
+
   protect_from_forgery with: :null_session
 
   rescue_from ActiveRecord::RecordInvalid, Mastodon::ValidationError do |e|
@@ -88,4 +90,8 @@ class Api::BaseController < ApplicationController
   def authorize_if_got_token!(*scopes)
     doorkeeper_authorize!(*scopes) if doorkeeper_token
   end
+
+  def set_cache_headers
+    response.headers['Cache-Control'] = 'no-cache, no-store, max-age=0, must-revalidate'
+  end
 end

app/controllers/api/v1/custom_emojis_controller.rb

@@ -3,6 +3,8 @@
 class Api::V1::CustomEmojisController < Api::BaseController
   respond_to :json
 
+  skip_before_action :set_cache_headers
+
   def index
     render_cached_json('api:v1:custom_emojis', expires_in: 1.minute) do
       ActiveModelSerializers::SerializableResource.new(CustomEmoji.local.where(disabled: false), each_serializer: REST::CustomEmojiSerializer)

app/controllers/api/v1/instances/activity_controller.rb

@@ -2,6 +2,7 @@
 
 class Api::V1::Instances::ActivityController < Api::BaseController
   before_action :require_enabled_api!
+  skip_before_action :set_cache_headers
 
   respond_to :json
 

app/controllers/api/v1/instances/peers_controller.rb

@@ -2,6 +2,7 @@
 
 class Api::V1::Instances::PeersController < Api::BaseController
   before_action :require_enabled_api!
+  skip_before_action :set_cache_headers
 
   respond_to :json
 

app/controllers/api/v1/instances_controller.rb

@@ -2,6 +2,7 @@
 
 class Api::V1::InstancesController < Api::BaseController
   respond_to :json
+  skip_before_action :set_cache_headers
 
   def show
     render_cached_json('api:v1:instances', expires_in: 5.minutes) do