Simplifies data constructor for primary keys in `join_keys` #292

All 367 tests pass in 16s

      1 files ±0     27 suites ±0 16s ⏱️ -3s
  367 tests ±0   367 ✔️ ±0 0 💤 ±0 0 ❌ ±0
1 016 runs ±0 1 016 ✔️ ±0 0 💤 ±0 0 ❌ ±0

Results for commit a76a140. ± Comparison against earlier commit 13e2325.