Support application/jwk-set+json content-type

[caioaao]

Some providers will return this content-type, which is just a JSON content-type with stronger guarantees, so it's safe to just treat it as regular JSON

https://webconcepts.info/concepts/media-type/application/jwk-set+json

[maennchen]

RFC for mime type: https://www.rfc-editor.org/rfc/rfc7517.html#section-8.5.1

[caioaao]

@maennchen seems like there's some instability in github's network, that's why the tests failed. It seems like I can't re-run them, though

[coveralls]

Pull Request Test Coverage Report for Build 177

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 1 (0.0%) changed or added relevant line in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.2%) to 92.188%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/oidcc_http_util.erl	0	1	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/oidcc_provider_configuration_worker.erl	1	96.3%

Totals
Change from base Build 171:	-0.2%
Covered Lines:	1062
Relevant Lines:	1152

---

💛 - Coveralls

[maennchen]

Thanks @caioaao ❤️