Fix concept-code lookups containing slashes
Summary
- percent-encode vocabulary IDs and concept codes as individual URL path segments
- preserve slash-containing ICD-O codes such as 8032/3 as a single route parameter
- add a regression test for the reported SDK request shape
The Node SDK was also rechecked: its production code already uses encodeURIComponent for both segments and its current test suite already covers a slash-containing concept code, so no Node change is needed.
Validation
- full testthat unit suite passed
- 64 live integration tests skipped because no API key was configured
- git diff --check
Summary by cubic
Fixes concept-code lookups in the R SDK so codes containing slashes (e.g., ICD-O code 8032/3) resolve correctly, including when hierarchy, synonym, relationship, or vocabulary-release query options are set. get_by_code now percent-encodes the vocabulary ID and concept code as individual URL path segments and treats literal percent sequences as literal segment input. The request builder preserves that encoding instead of letting query updates decode it.
This mirrors the Node SDK and adds regression tests covering the encoded request path with and without query options.