This commit introduces support for AccountMigration federation message
receive. It covers the cases when the new home pod for a user is remote
respective to the recepient pod of the message. It also allows to initiate
migration locally by a podmin from the rails console. This will give the
pods a possibility to understand the account migration event on the
federation level and thus future version which will implement migration
will be backward compatible with the pods starting from this commit.

See #7234

Otherwise Rails 5 would ignore the migration version and create the
tables with bitints as IDs on MySQL.

we released that in 0.5.0.0 in 2015, we do not support skipping majors
anyway, and this is broken in Rails 5, so let's remove this. If people
upgrade from before 0.5.0.0, they have to upgrade via 0.6.0.0, but
that's written in the documenation.

Although this is contrary to rails best-practises, we cannot provide a schema.rb that works for both MySQL and PostgreSQL, so we have no choice. Our migrations are maintained, so it should always be possible to get back to a "clean" database schema anyway.

... this breaks the Rails 5 upgrade, and it's actually no longer needed.
New installations will have the right size anyway, and even if some
older installations miss the migration by not updating for 2 years, it
still doesn't matter since there is no risk that we will ever have
emojis in our migration filenames.

Related to #36

closes #7158

fixes #4319

closes #7118

Turns out that postgres can't handle "0" as boolean, but mysql can
handle "false".

closes #7115#pullrequestreview-699342

Also fixed the "fix public photos"-migration, because it didn't work
with migration-models :/

fixes #6177

Also remove confirm_email_token when unconfirmed_email is removed.

Fixes #7048

closes #7051

closes #7043

related to #7032

Signed-off-by: Lukas Matt <lukas@zauberstuhl.de>

closes #7038

The same as #7009 but now all of them ;)

Before #6873 we deleted contacts when someone blocks a person, but we
didn't drop the notification for the started sharing event. In #6864
we try to get the contact for the notification, which is not there
anymore.

So we need to remove the notifications for the contacts that don't exit
anymore.

fix #6857

delete invitations-table (and constraints) before deleting the users

otherwise the counter goes into negative ;)

also  reset all negative counters

This migrations runs only if the old 20150404193023_participation_counter
migration has not been run.

The new migration is a lot faster, because it runs after the
participation-cleanup migration has been run, so the participation table
is now a lot smaller for people upgrading from 0.5.x to 0.6.x.

It also doesn't remove manually created participations (without likes,
comments or poll participations on the same post).

Fixes #6786

* remove author_signature column
* delete all self-participating participations
* delete all participations where author and post-author are remote
* delete all duplicate participations
* delete all participations without post
* create unique index

* conversations
* messages
* photos
* polls
* poll answers
* poll participations

fixes #4697

Following query takes over 20 minutes and fills up the database:
SELECT * FROM participations WHERE author_id = XXXXX

On servers with a huge participations-table this is a serious
performance issue which is easily fixed by the author_id index

Signed-off-by: Lukas Matt <lukas@zauberstuhl.de>