Set snowflake IDs for backdated statuses (#5260)

- Rename Mastodon::TimestampIds into Mastodon::Snowflake for clarity
- Skip for statuses coming from inbox, aka delivered in real-time
- Skip for statuses that claim to be from the future

app/lib/activitypub/activity.rb

@@ -3,10 +3,11 @@
 class ActivityPub::Activity
   include JsonLdHelper
 
-  def initialize(json, account)
+  def initialize(json, account, options = {})
     @json    = json
     @account = account
     @object  = @json['object']
+    @options = options
   end
 
   def perform
@@ -14,9 +15,9 @@ class ActivityPub::Activity
   end
 
   class << self
-    def factory(json, account)
+    def factory(json, account, options = {})
       @json = json
-      klass&.new(json, account)
+      klass&.new(json, account, options)
     end
 
     private

app/lib/activitypub/activity/announce.rb

@@ -15,8 +15,9 @@ class ActivityPub::Activity::Announce < ActivityPub::Activity
       account: @account,
       reblog: original_status,
       uri: @json['id'],
-      created_at: @json['published'] || Time.now.utc
+      created_at: @options[:override_timestamps] ? nil : @json['published']
     )
+
     distribute(status)
     status
   end

app/lib/activitypub/activity/create.rb

@@ -43,7 +43,7 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
       text: text_from_content || '',
       language: language_from_content,
       spoiler_text: @object['summary'] || '',
-      created_at: @object['published'] || Time.now.utc,
+      created_at: @options[:override_timestamps] ? nil : @object['published'],
       reply: @object['inReplyTo'].present?,
       sensitive: @object['sensitive'] || false,
       visibility: visibility_from_audience,