Fix body sending by allowing serializing strings

[sarroutbi]

This patch refactors the resilient_client to fix a JSON double-encoding bug that caused the verifier to reject requests.

The root cause of the "malformed parameters" error from Verifier was that the get_json_request function was being called with a String that already contained JSON. The function would then re-serialize this string, wrapping it in an extra layer of quotes and escaping its contents, leading to a double-encoded payload.

This PR resolves the issue by improving the client's API to be more explicit and prevent this error by design.

• keylime/src/resilient_client.rs:

The original get_json_request function has been refactored. Its signature is changed to accept a pre-serialized string slice (json_string: &str) and it now uses this string directly as the request body without further serialization.

A new function, get_json_request_from_struct<T: Serialize>, has been introduced. This function now contains the original logic: it takes a serializable Rust struct, converts it to a JSON string, and then calls the new get_json_request to build the request.

• keylime-push-model-agent/src/attestation.rs & keylime/src/registrar_client.rs:

All call sites have been updated to use the new, more descriptive get_json_request_from_struct function, clarifying the intent to serialize a struct.

A test case in the push-model agent was also corrected to assert against the properly single-encoded JSON body.

[codecov]

Codecov Report

Attention: Patch coverage is 38.46154% with 16 lines in your changes missing coverage. Please review.

Project coverage is 58.37%. Comparing base (f050222) to head (3bb71bc).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
keylime/src/resilient_client.rs	50.00%	10 Missing ⚠️
keylime/src/registrar_client.rs	0.00%	5 Missing ⚠️
keylime-push-model-agent/src/attestation.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

Flag	Coverage Δ
e2e-testsuite	58.37% <38.46%> (-0.07%)	⬇️
upstream-unit-tests	58.37% <38.46%> (-0.07%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
keylime-push-model-agent/src/attestation.rs	41.13% <0.00%> (ø)
keylime/src/registrar_client.rs	78.70% <0.00%> (-1.22%)	⬇️
keylime/src/resilient_client.rs	48.68% <50.00%> (+0.35%)	⬆️

... and 4 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[sergio-correia]

Thanks, LGTM