* ActivityPub migration procedure

Once one account is detected as going from OStatus to ActivityPub,
invalidate WebFinger cache for other accounts from the same domain

* Unsubscribe from PuSH updates once we receive an ActivityPub payload

* Re-subscribe to PuSH unless already unsubscribed, regardless of protocol

* i18n: Minor changes in Polish translation

* i18n: pl

flex-basis: 0 allows make flexbox smaller than its contents on Safari <10.

https://github.com/philipwalton/flexbugs#1-minimum-content-sizing-of-flex-items-not-honored

* Handle duplicate ActivityPub activities

Only perform side-effects when record processed for the first time

* Fast-forward repeat follow requests

New strings added to be shown on the new profile page

*Note: OStatus URIs are invalid for ActivityPub. But we have them for
as long as we want to keep old OStatus-sourced content and as long as
we remain OStatus-compatible.*

- In Announce handling, if object URI is not a URL, fallback to object URL
- Do not use specialized ThreadResolveWorker, rely on generalized handling
- When serializing notes, if parent's URI is not a URL, use parent's URL

* use existing inflections instead of custom helper

* use ActiveSupport versions

* Show what protocol used for in admin/accounts#index

* Add frozen_string_literal

* i18n: Update Polish translation

* Update pl.json

* Redesign public profiles

* Responsive design

* Change public profile status filtering defaults and add options

- No longer displays private/direct toots even if you are permitted access
- By default omits replies
- "With replies" option
- "Media only" option

* Redesign account grid cards

* Fix style issues

* Make share intent modal to make "signed in as" shown.

* fix glitch on mobile.

Update: new string + more translations for the time in words

* Add protocol field
* Switch protocol specific information according to active protocol
* Hide PuSH subscription related buttons if ActivityPub is active

* Add support for searching AP users

* use JsonLdHelper

* Add protocol handler. Handle follow intents

* Add share intent

* Improve code in intents controller

* Adjust share form CSS

* Deliver ActivityPub Like

* Deliver ActivityPub Undo-Like

* Deliver ActivityPub Create/Announce activities

* Deliver ActivityPub creates from mentions

* Deliver ActivityPub Block/Undo-Block

* Deliver ActivityPub Accept/Reject-Follow

* Deliver ActivityPub Undo-Follow

* Deliver ActivityPub Follow

* Deliver ActivityPub Delete activities

Incidentally fix #889

* Adjust BatchedRemoveStatusService for ActivityPub

* Add tests for ActivityPub workers

* Add tests for FollowService

* Add tests for FavouriteService, UnfollowService and PostStatusService

* Add tests for ReblogService, BlockService, UnblockService, ProcessMentionsService

* Add tests for AuthorizeFollowService, RejectFollowService, RemoveStatusService

* Add tests for BatchedRemoveStatusService

* Deliver updates to a local account to ActivityPub followers

* Minor adjustments