Admin accounts controller cleanup (#1664)

* Remove unused account_params method in admin/accounts controller

* Introduce AccountFilter to find accounts

* Use AccountFilter in admin/accounts controller

* Use more restful routes admin silence and suspension area

* Add admin/silences and admin/suspensions controllers

app/models/account_filter.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+class AccountFilter
+  attr_reader :params
+
+  def initialize(params)
+    @params = params
+  end
+
+  def results
+    scope = Account.alphabetic
+    params.each do |key, value|
+      scope = scope.merge scope_for(key, value)
+    end
+    scope
+  end
+
+  def scope_for(key, value)
+    case key
+    when /local/
+      Account.local
+    when /remote/
+      Account.remote
+    when /by_domain/
+      Account.where(domain: value)
+    when /silenced/
+      Account.silenced
+    when /recent/
+      Account.recent
+    when /suspended/
+      Account.suspended
+    else
+      raise "Unknown filter: #{key}"
+    end
+  end
+end