Restful refactor of accounts/ routes (#2133)

* Add routing specs for accounts followers and following actions

* Use more restful route naming for public account follow pages

Moves two actions:
- accounts#followers to accounts/follower_accounts#index
- accounts#following to accounts/following_accounts#index

Adds routing spec to ensure prior URLs are preserved.

spec/requests/link_headers_spec.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe 'Link headers' do
+  describe 'on the account show page' do
+    let(:account) { Fabricate(:account, username: 'test') }
+
+    before do
+      get short_account_path(username: account)
+    end
+
+    it 'contains webfinger url in link header' do
+      link_header = link_header_with_type('application/xrd+xml')
+
+      expect(link_header.href).to match 'http://www.example.com/.well-known/webfinger?resource=acct%3Atest%40cb6e6126.ngrok.io'
+      expect(link_header.attr_pairs.first).to eq %w[rel lrdd]
+    end
+
+    it 'contains atom url in link header' do
+      link_header = link_header_with_type('application/atom+xml')
+
+      expect(link_header.href).to eq 'http://www.example.com/users/test.atom'
+      expect(link_header.attr_pairs.first).to eq %w[rel alternate]
+    end
+
+    def link_header_with_type(type)
+      response.headers['Link'].links.find do |link|
+        link.attr_pairs.any? { |pair| pair == ['type', type] }
+      end
+    end
+  end
+end