Move create/destroy actions for api/v1/statuses to namespace (#3678)

Each of mute, favourite, reblog has been updated to:

- Have a separate controller with just a create and destroy action
- Preserve historical route names to not break the API
- Mild refactoring to break up long methods

spec/controllers/api/v1/statuses/mutes_controller_spec.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe Api::V1::Statuses::MutesController do
+  render_views
+
+  let(:user)  { Fabricate(:user, account: Fabricate(:account, username: 'alice')) }
+  let(:app)   { Fabricate(:application, name: 'Test app', website: 'http://testapp.com') }
+  let(:token) { double acceptable?: true, resource_owner_id: user.id, application: app }
+
+  context 'with an oauth token' do
+    before do
+      allow(controller).to receive(:doorkeeper_token) { token }
+    end
+
+    describe 'POST #create' do
+      let(:status) { Fabricate(:status, account: user.account) }
+
+      before do
+        post :create, params: { status_id: status.id }
+      end
+
+      it 'returns http success' do
+        expect(response).to have_http_status(:success)
+      end
+
+      it 'creates a conversation mute' do
+        expect(ConversationMute.find_by(account: user.account, conversation_id: status.conversation_id)).to_not be_nil
+      end
+    end
+
+    describe 'POST #destroy' do
+      let(:status) { Fabricate(:status, account: user.account) }
+
+      before do
+        user.account.mute_conversation!(status.conversation)
+        post :destroy, params: { status_id: status.id }
+      end
+
+      it 'returns http success' do
+        expect(response).to have_http_status(:success)
+      end
+
+      it 'destroys the conversation mute' do
+        expect(ConversationMute.find_by(account: user.account, conversation_id: status.conversation_id)).to be_nil
+      end
+    end
+  end
+end