Fix resolving accounts sometimes creating duplicate records for a given AP id (#15364)

* Fix ResolveAccountService accepting mismatching acct: URI

* Set attributes that should be updated regardless of suspension

* Fix key fetching

* Automatically merge remote accounts with duplicate `uri`

* Add tests

* Add "tootctl accounts fix-duplicates"

Finds duplicate accounts sharing a same ActivityPub `id`, re-fetch them and
merge them under the canonical `acct:` URI.

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/workers/account_merging_worker.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+class AccountMergingWorker
+  include Sidekiq::Worker
+
+  sidekiq_options queue: 'pull'
+
+  def perform(account_id)
+    account = Account.find(account_id)
+
+    return true if account.nil? || account.local?
+
+    Account.where(uri: account.uri).where.not(id: account.id).find_each do |duplicate|
+      account.merge_with!(duplicate)
+      duplicate.destroy
+    end
+  end
+end