fix: improve json handling on wrong or missing contenttype

[SaturnFromTitan]

Related Issue: #291

Type of change:

• Bug fix (non-breaking change which fixes an issue)

Description:

• When users set datacontenttype to something like application/octet-stream but pass a dict as data, the JSONFormatter now produces JSON-decodable output.
• The spec states that when datacontenttype is unspecified, processing SHOULD proceed as if it were application/json.

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Pre-submission checklist:

• I have read the CONTRIBUTING.md file.
• I have signed off my commits using git commit --signoff.
• I have added tests that prove my fix is effective or that my feature works.
• I have updated the documentation (README.md, CHANGELOG.md, etc.) as necessary.
• I have run pre-commit and tox and all checks pass.
• This pull request is ready to be reviewed.

[SaturnFromTitan]

@xSAVIKx do you see why the tests are not running in this PR?

[xSAVIKx]

@xSAVIKx do you see why the tests are not running in this PR?

that's default behavior of github - workflows are halted until a maintainer allows them to run in a PR. Just did that

[SaturnFromTitan]

@xSAVIKx thanks! it's ready for review now ✌️

[SaturnFromTitan]

@xSAVIKx i can't seem to merge the PR - can you please? (feel free to ignore this message if you intentionally wait to merge this PR)