Related to swh/meta#4959

This fixes python 3.7 support due to poetry, a dependency of isort, that
removed support for that Python version in a recent release.

The existing type, {obj_id: content} did not allow composite obj_ids,
because composite obj_ids are dicts so they are not hashable.

this actually requires quite some refactoring in the seaweedfs backend,
mostly to support the (somewhat useless) `list_content()` and iterator methods.

This method is mostly used for tests, and since we do not have any upper hard
limit, it does not make it more dangerous to accept unlimited calls to this
method, which on the other hand can be handy for tests with an
objstorage having more objects than the DEFAULT_LIMIT value.

In order to remove warnings about /apidoc/*.rst files being included
multiple times in toc when building full swh documentation, prefer to
include module indices only when building standalone package documentation.

Also include them the proper sphinx way.

Related to T4496

In addition to add support for multi-hashes, we will need to use more advanced
features of the Azure Blob Storage, so using only mock-based tests will be
less reliable.

This commit adds the option to run the test suite with Azurite, a clone
of the Azure Blob Storage API, which is a standard tool used in tests.

- pre-commit from 4.1.0 to 4.3.0,
- codespell from 2.2.1 to 2.2.2,
- black from 22.3.0 to 22.10.0 and
- flake8 from 4.0.1 to 5.0.4. Also freeze flake8 dependencies.

Also change flake8's repo config to github (the gitlab mirror
being outdated).

To conform to the existing signature

They are not used anywhere

For now, any hash algo other than ID_HASH_ALGO ("sha1") is ignored.

This changes the network protocol used by `list_content` from a
concatenation of fixed-length hashes to a stream of msgpacked
dictionaries.

Like WineryObjStorage and other ObjStorage backends.

It is not used anywhere (and swh-storage provides content_get_random() that
feels the same need), and cloud backends do not implement it anyway.

And this is necessary to make the function type-check.

It is not used anymore.

The return value was useless, as the same ObjId has to be passed as argument.

And as far as I can tell, no other package depends on this return value.

Like other backends.

Allowing None will be an issue once we add type annotations to
methods which use self.compression.

For consistency with ObjStorage.add()

In practice, it is not very useful to recompute it in the objstorage,
as callers already know it.

That hook can be frustrating as it can discard a long commit message
if it finds a typo in it so better removing it.

Related to T3922

black is considered stable since release 22.1.0 and the version
we are currently using is quite outdated and not compatible with
click 8.1.0, so it is time to bump it to its latest stable release.

Please note that E501 pycodestyle warning related to line length
is replaced by B950 one from flake8-bugbear as recommended by black.
https://black.readthedocs.io/en/stable/the_black_code_style/current_style.html#line-length

Related to T3922

Do not yield an empty byte in list_content as it triggers an error
since the release of werkzeug 2.1.0 which bumps HTTP protocol version
from 1.0 to 1.1.

Ensure objstorage is initialized in streaming responses implementation,
if no POST requests on other endpoints have been issued the global
variable objstorage was still equal to None.

Closes T4119

pytest-postgresql 3.1.3 and pytest-redis 2.4.0 added support for
pytest >= 7 so we can now drop the pytest pinning.

Due to test modules being copied in subdirectories of the
build directory by setuptools, it makes pytest fail by raising
ImportPathMismatchError exceptions when invoked from root
directory of the module.

So ignore the build folder to discover tests.

`bool(objstorage)` uses `len(objstorage) != 0`, which takes "a little bit"
of time on non-trivial objstorages...

app.config contains flask internals such as DEBUG, so we should avoid
stomping on it entirely.