HTTP signatures (#4146)

* Add Request class with HTTP signature generator

Spec: https://tools.ietf.org/html/draft-cavage-http-signatures-06

* Add HTTP signature verification concern

* Add test for SignatureVerification concern

* Add basic test for Request class

* Make PuSH subscribe/unsubscribe requests use new Request class

Accidentally fix lease_seconds not being set and sent properly, and
change the new minimum subscription duration to 1 day

* Make all PuSH workers use new Request class

* Make Salmon sender use new Request class

* Make FetchLinkService use new Request class

* Make FetchAtomService use the new Request class

* Make Remotable use the new Request class

* Make ResolveRemoteAccountService use the new Request class

* Add more tests

* Allow +-30 seconds window for signed request to remain valid

* Disable time window validation for signed requests, restore 7 days
as PuSH subscription duration (which was previous default due to a bug)

app/models/account.rb

@@ -130,7 +130,7 @@ class Account < ApplicationRecord
   end
 
   def subscription(webhook_url)
-    OStatus2::Subscription.new(remote_url, secret: secret, lease_seconds: 86_400 * 30, webhook: webhook_url, hub: hub_url)
+    OStatus2::Subscription.new(remote_url, secret: secret, lease_seconds: 30.days.seconds, webhook: webhook_url, hub: hub_url)
   end
 
   def save_with_optional_media!

app/models/concerns/remotable.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 module Remotable
-  include HttpHelper
   extend ActiveSupport::Concern
 
   included do
@@ -20,7 +19,7 @@ module Remotable
         return if !%w(http https).include?(parsed_url.scheme) || parsed_url.host.empty? || self[attribute_name] == url
 
         begin
-          response = http_client.get(url)
+          response = Request.new(:get, url).perform
 
           return if response.code != 200
 

app/models/subscription.rb

@@ -16,8 +16,8 @@
 #
 
 class Subscription < ApplicationRecord
-  MIN_EXPIRATION = 7.days.seconds.to_i
-  MAX_EXPIRATION = 30.days.seconds.to_i
+  MIN_EXPIRATION = 1.day.to_i
+  MAX_EXPIRATION = 30.days.to_i
 
   belongs_to :account, required: true