Related T2793

Add rsync which was implicit dependency for docker dev setup.
Move comments so that the command is runnable as-is.

Related T2793

include a first entry about ongoing crawl pause

Closes T2460

Related to T2762

They are now generated by Plantuml, so it needs to be called.

also enable displaying TODO by defaults, as this is devel-oriented doc

this allows to have full support for all sphinx directives and link types

replaces previous use of plain CommonMark parsing

Related to T2610

Related to T2610

flake8 hook has been removed from https://github.com/pre-commit/pre-commit-hooks
so now use the one from https://gitlab.com/pycqa/flake8

- postgresql-server-dev-all was overkill, postgresql libpq-dev suffice
- short description on deps grouped by role

They are needed for the documentation.

- pre-commit doesn't necessarily exist as a system package (i.e.
Debian buster), and is used as a Python library in swh git repos,
so install via pip in the virtualenv.
- install local swh packages as a 2-step process to avoid errors

The lister no longer creates Origin objects.

- add the indexer journal client
- replace the Ceph logo with (Open)ZFS one
- add the MDStorage
- add Vault workers and their RPC link to the Storage and Vault API

Related to T2105

Reviewers: #reviewers

Differential Revision: https://forge.softwareheritage.org/D3634

Summary:
If running this command on bullseye, there may already be a postgresql-12-server
installed; so pytest-postgresql will try to use postgresql-12's pg_ctl, which
does not exist.

Using the virtual package 'postgresql' instead of 'postgresql-11' installs
the right version for the distribution.

Reviewers: #reviewers, olasd

Differential Revision: https://forge.softwareheritage.org/D3631

Reviewers: #reviewers

Differential Revision: https://forge.softwareheritage.org/D3630

This reverts commit b5d50d89.

This only worked because I have a local postgresql on which I'm superuser,
apparently.