[#647] tests for web push

config/test.exs

lib/pleroma/web/mastodon_api/mastodon_api_controller.ex

lib/pleroma/web/mastodon_api/subscription_controller.ex

lib/pleroma/web/mastodon_api/views/push_subscription_view.ex

lib/pleroma/web/push/impl.ex

lib/pleroma/web/push/push.ex

lib/pleroma/web/push/subscription.ex

lib/pleroma/web/router.ex

test/support/factory.ex

test/support/web_push_http_client_mock.ex

test/web/mastodon_api/push_subscription_view_test.exs

test/web/mastodon_api/subscription_controller_test.exs

test/web/push/impl_test.exs