FI-3155 Fix JWT encoding method

[alisawallace]

Summary

This PR updates the test kit to use the Base64.encode64/decode64 methods for the X.509 certs in the JWTs, instead of the original Base64.urlsafe_encode64/decode64 methods that resulted in JWTs whose signature could not be verified, causing tests to always fail.

Testing Guidance

I originally discovered and fixed the bug using the presets in the following branch: https://github.com/inferno-framework/udap-security-test-kit/tree/udaped-partial-demo

However, any valid registration inputs (including Inferno's test certs) can be used to run the Dynamic Client Registration test group and demonstrate the issue.
The software statement JWT can be grabbed from the HTTP request or the test output for test 1.2.03 registration success and pasted into jwt.io. Before changing the encode method, it will say "Signature verification failed", but after the signature verification will succeed. Also, if using the partial demo presets, the test itself should "fail" with a 200 response code instead of a 400 saying "Missing validation result."

[alisawallace]

I ran bundle update before making these changes, and as a result two spec tests for generate_client_certs, unrelated to the JWT encoding change, are now failing due to what I believe are changes in how core handles null inputs. I'm not sure how to resolve this, @Jammjammjamm could you advise?

[Jammjammjamm]

The test isn't required anywhere in the actual test kit, so it isn't loaded into the test repository. So the spec is currently testing dead code, which is a bit odd. If this test and spec are worth keeping, you can change the definition of runnable to just be described_class rather than finding it through the repository.

[alisawallace]

The test isn't required anywhere in the actual test kit, so it isn't loaded into the test repository. So the spec is currently testing dead code, which is a bit odd. If this test and spec are worth keeping, you can change the definition of runnable to just be described_class rather than finding it through the repository.

I see now, the generate_client_certs_test is less dead and more temporarily asleep, since this is a feature we plan to add back in the future once our certs are up to snuff (I believe we have a ticket for it), but took out in the meantime for release. To keep it simple I just added this as a requirement to the dynamic client registration group where it was used and will be used in the future, and that fixed the tests without needing to redefine runnable.

[Jammjammjamm]

Whoops!

[Jammjammjamm]

Wait, why is this changing? I see spec.add_runtime_dependency everywhere else.

[alisawallace]

I think this was a Rubocop auto-correction. When I revert it back to the original my editor gives me a blue squiggly line and says:

Gemspec/AddRuntimeDependency: Use add_dependency instead of add_runtime_dependency.RuboCopGemspec/AddRuntimeDependency

I saw you approved the PR but from this comment can't tell if you changed your mind, so @Jammjammjamm just confirm if I'm good to go or if you want me to revert to spec.add_runtime_dependency!

[Jammjammjamm]

Gotcha, it's good to go.