Add header with API version

[renghen]

Closes #249

Please check if the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• CHANGELOG.md have been updated (for bug fixes / features / docs)

What kind of change does this PR introduce?

Feature

What is the current behavior?

See #249

What is the new behavior?

The 'x-reduct-api' header is added with the API version for each response

Does this PR introduce a breaking change?

No

Other information:

[atimin]

@rengehn , thanks for your contribution! See my comment about the implementation.

Don't forget, please, to add a record into CHANGELOG.md and a test into api_tests/http_test.py.

P.S. And fill please the PR template, so that we could keep the context. Thanks!

[atimin]

@renghen , the code looks good for me. I resolved conflicts with the main branch and ready to merge, but the linter fails. Could you make the checks green? Use cargo fmt to fix the format automatically. Thanks!

[atimin]

Just figured out that I need it urgently. I've taken it with the broken CI but I'll fix it in the main branch.

[renghen]

I did a cargo fmt before any push, I need to check what goes wrong on that one

[renghen]

I got it, I should use
cargo fmt --all for it to be ok.
cargo fmt is not enough
I did not know that.