Refactor of API timeline actions (#3263)

- Increase coverage to exercise all parts of each action
- Move into namespace to share common code
- Misc refactor of each action for smaller methods, simpler code

spec/controllers/api/v1/timelines/public_controller_spec.rb

@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe Api::V1::Timelines::PublicController do
+  render_views
+
+  let(:user)  { Fabricate(:user, account: Fabricate(:account, username: 'alice')) }
+
+  before do
+    allow(controller).to receive(:doorkeeper_token) { token }
+  end
+
+  context 'with a user context' do
+    let(:token) { double acceptable?: true, resource_owner_id: user.id }
+
+    describe 'GET #show' do
+      before do
+        PostStatusService.new.call(user.account, 'New status from user for federated public timeline.')
+      end
+
+      it 'returns http success' do
+        get :show
+
+        expect(response).to have_http_status(:success)
+        expect(response.headers['Link'].links.size).to eq(2)
+      end
+    end
+
+    describe 'GET #show with local only' do
+      before do
+        PostStatusService.new.call(user.account, 'New status from user for local public timeline.')
+      end
+
+      it 'returns http success' do
+        get :show, params: { local: true }
+
+        expect(response).to have_http_status(:success)
+        expect(response.headers['Link'].links.size).to eq(2)
+      end
+    end
+  end
+
+  context 'without a user context' do
+    let(:token) { double acceptable?: true, resource_owner_id: nil }
+
+    describe 'GET #show' do
+      it 'returns http success' do
+        get :show
+
+        expect(response).to have_http_status(:success)
+        expect(response.headers['Link']).to be_nil
+      end
+    end
+  end
+end