Dependency fixes from #101

- avoid recompiling requirements files

- fix package data issue with sdist
- install & configure tox for testing under py3.7-3.10
- add testdir config so raw `pytest` works

- upstream: https://github.com/PyCQA/flake8/pull/1438
- pip-compile doesn't support env specifiers, so need to run it
under Python3.7. Enforce that via Makefile.

[WIP] S3 fixes and improvements

Use the new S3 content integrity support [1] to pass the object sha256
to S3 when uploading objects, so S3 can confirm integrity.

[1] https://docs.aws.amazon.com/AmazonS3/latest/userguide/checking-object-integrity.html

- move dev-requirements to "latest"
- upgrade reequirements sensibly
- fix minor azure typing issues
- azure test fixes wrt URL changes (/bucket/prefix%2Frepo%2Forg%2Fsha -> /bucket/prefix/repo/org/sha)

git-lfs as of v2.5.0 [1] detects the file Content-Type and provides it
during PUT requests to the storage when using the basic transfer. If we
don't include the same `Content-Type` value in the S3 signature
generation, then S3 rejects it during upload.

Unfortunately git-lfs doesn't pass the `Content-Type` value to the Batch
request, so it can't be included in S3 signature generation. And while
setting `lfs.contenttype=false` in the client config forces sending
`application/octet-stream` [2], S3 isn't happy with that either.

If the Batch response upload action includes a `Content-Type` header
then git-lfs will always use that for the PUT request, so always return
`application/octet-stream`, and also use it for signature generation.

[1] https://github.com/git-lfs/git-lfs/pull/3137
[2] https://github.com/git-lfs/git-lfs/pull/3163

Replace use of os.path.join (which exhibits platform dependent behaviour) with posixpath.join where necessary

Bump urllib3 from 1.26.4 to 1.26.5

basic_streaming transfer adapter handling of 'filename' URL parameter

This guarantees that join() will be performed using forward slashes.

'filter' the 'filename' URL parameter through 'safe_filename' IF it was actually sent with the request

It seems this URL parameter is not always passed by clients.
Out of my two setups, the windows based one does not, which led me to investigate.
    git version 2.31.1.windows.1 using ssh to clone a repository with lfs.url=http://...     - URL parameter not passed, hitting the failure mode mitigated by this PR
    git version 2.31.1 using a local file path to clone a repository with lfs.url=http://...   - Everything is fine
I have not investigated yet whether the URL parameter passing differences are by design or by accident, however it seems prudent for the transfer adapter to cleanly handle this case.

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.4 to 1.26.5.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](https://github.com/urllib3/urllib3/compare/1.26.4...1.26.5

)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

Handle Content-Type and Content-Disposition headers

Sometimes when requesting a file from Giftless we don't want it to
receive it as an attachment, eg when loading it in a browser JS widget
or embedding it. This change adds support for a `x-disposition` extra
which storage backends can use to set the appropiate headers when
returning a download URL.

As we don't have the actual file name that the mimetype module can use

Also return a default value of `application/octet-stream` on
the`get_mime_type()` method

Bump urllib3 from 1.26.2 to 1.26.4

This is currently inferred from the filename using `mimetypes`

Added new `get_mime_type()` method to `StreamingStorage` so that
different backends can implement it. For local storage we use the
builitin `mimetypes` module to guess the mime type from the filename,
for Azure we get it from the blob properties.

In the basic streaming transfer handler we read the value of this method
and add it to the `Content-type` header.

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.2 to 1.26.4.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](https://github.com/urllib3/urllib3/compare/1.26.2...1.26.4

)

Signed-off-by: dependabot[bot] <support@github.com>

Upgrade requirements

Bump pyyaml from 5.3.1 to 5.4

Bump pygments from 2.7.3 to 2.7.4

Bumps [pygments](https://github.com/pygments/pygments) from 2.7.3 to 2.7.4.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](https://github.com/pygments/pygments/compare/2.7.3...2.7.4

)

Signed-off-by: dependabot[bot] <support@github.com>

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 5.3.1 to 5.4.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](https://github.com/yaml/pyyaml/compare/5.3.1...5.4

)

Signed-off-by: dependabot[bot] <support@github.com>

Bump jinja2 from 2.11.2 to 2.11.3

Bumps [jinja2](https://github.com/pallets/jinja) from 2.11.2 to 2.11.3.
- [Release notes](https://github.com/pallets/jinja/releases)
- [Changelog](https://github.com/pallets/jinja/blob/master/CHANGES.rst)
- [Commits](https://github.com/pallets/jinja/compare/2.11.2...2.11.3

)

Signed-off-by: dependabot[bot] <support@github.com>

Implement S3 storage class for Streaming and External basic transfer adapters