closes #8037

Person.find_or_fetch_by_identifier raises an exception if person is not found localy and not fetchable. It never returns nil. These code changes take care about this behaviour and changes specs and code to behave equally.

Also related to #8253

Only delete photos older than a day, so we don't delete photos for posts
which were uploaded 10 minutes ago and the author is still writing the
post for it.

closes #8041

Facebook removed the API and facebook integration is broken now, so lets
remove it.

closes #7874

closes #7705

Fixes #5727

closes #7624

fixes #1649

closes #7629

Introduce Workers::Mail::NotifierBase to be a base for all appropriate
mail workers to reduce code duplication

closes #7223

closes #7158

closes #7050

Fixes #5116

and delete old batch worker and receiver

* add port to pods
* remove url from person and link people with pod-table

add tooltips in the frontend
fix a JS problem with empty hostname
use `find_in_batches` correctly
add a migration to clean up the pods table + unique index on hostname

* add a class for checking pod connectivity
* extend pod model to handle new functionality
* add an admin frontend to list pods and re-trigger checks manually
* add a daily worker to run through all the pods
* add unit tests for most of the new code

* .well-known/social-relay - to serve subscription preferences to relays
* Workers.deferred_dispatch relay carbon copy functionality for outbound sending

See discussion here: https://www.loomio.org/d/9vpoe0UR/public-post-federation#comment-730911 and spec here: https://wiki.diasporafoundation.org/Relay_servers_for_public_posts

closes #6168

closes #5983

closes #5960

It seems ActiveRecord ignores .limit() if .find_each() is used to iterate the query (http://stackoverflow.com/a/6680541/1489738). Using .each() instead. Added a test.

closes #5953

Fixes #5834