And cleanup old reshares with deleted root posts

closes #7578

closes #7576

Fixes #7424

closes #7575

closes #7568

Fixes #7563

closes #7566

closes #7579

This was in all stack traces, which confused people ...

We currently only support IE11, so the version check was already old
again ...

When we break old browser versions, we don't check that for other
browsers. So older IE browser just break, like very other older browser
too.

closes #7557

closes #7551

closes #7530

[ci skip]

closes #7465

closes #7446

closes #7295

closes #7473

closes #6589

fixes #7195

closes #7455

[ci skip]

Fixes #7421

closes #7447

This changes links from /posts/:id to /posts/:guid where the links are
not clicked very often. ID search is faster than guid search so we can't
change it everywhere, but these links are not very useful for clicking,
but can be used for easier guid look up.

closes #7453

Fixes #7363

closes #7452

Breaking a public key of a person can be used to "block" receiving posts
from this person on the pod. So we should handle that case better and
not just trigger many retries for something that will fail again.

closes #7448

This is now broken since more than half a year, so I think we can just
remove it.

Podmins shouldn't use this anyway, because it does bad things, like
replacing NULL with an empty string when editing something. If we really
need an admin interface for something, we should add it to our own admin
panel at /admins/dashboard.

Fixes #7027 and #6413

closes #7440

Fixes #7249

closes #7420

Fixes #7438. The regression has possibly been introduced by #7207.

closes #7441

closes #7429

fixes #7427

[ci skip]

closes #7414

closes #7367

"should see JSON"

closes #7410

closes #7401

Since 4.2.3 sidekiq allows to disable its own session cookie for the
case where the app provides a session already.

closes #7395

These lines might have been necessary some time ago but now they are making things worse.

closes #7374