fix: preserves caller-provided plain PHP objects in request params (closes #392)

[Justin Hammond (Justintime50)]

Description

• Preserves caller-provided plain PHP objects in request params so (object) [] is sent as an empty JSON object ({}) instead of being stringified (closes 8.8.2: empty PHP arrays now reach the API as JSON arrays where objects are expected — request rejected with no pointer to the cause #392)

Testing

Added new unit tests that ensure backwards compatibility along with the change of standard objects being encoded properly with the fix.

Pull Request Type

Please select the option(s) that are relevant to this PR.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement (fixing a typo, updating readme, renaming a variable name, etc)