fix(models): handle missing primary field when deserializing Role (signed re-push of #44)

[shiftcontrol-dan]

Summary

Signed re-push of @travipross' commit from #44 (that commit carried an S/MIME signature from an internal CA that GitHub reports as no_user, so it could not satisfy the signed-commits rule on main), plus an end-to-end regression test, a version bump, and changelog notes.

Role::primary gains #[serde(default)]. Applying deserialize_with suppresses serde's implicit handling of omitted Option<T> fields, so without an accompanying default a payload that simply omits primary was rejected with a missing field error rather than deserializing to None. This regressed 0.3 behaviour during the 0.4.x lenient-bool work.

#[serde(
    default, // required as `deserialize_with` does not set default when field is missing
    skip_serializing_if = "Option::is_none",
    deserialize_with = "deserialize_optional_lenient_bool"
)]
pub primary: Option<bool>,

Tests

Carried over from #44:

• role_deserialization_with_omitted_primary_key — minimal reproduction isolating the bug to Role.
• Six unit tests on deserialize_optional_lenient_bool in src/utils/serde.rs, including omitted_key_fails_without_serde_default, which pins the reason default is required at the call site.

Added here:

• deserialize_github_enterprise_user_list, driven by a new src/test_data/github_enterprise_user_list_test.json fixture. This is the sanitized real GitHub Enterprise SCIM /Users response @travipross supplied in this comment. The first resource carries a role with primary absent ({"value": "enterprise_owner"}), the second an empty roles array. It exercises the failure at the ListResponse level, which is where it actually bit.

Both regression tests were confirmed to fail against the unfixed code, with the reported error:

role_deserialization_with_omitted_primary_key ... FAILED
  missing field `primary`, line: 1, column: 26
deserialize_github_enterprise_user_list ... FAILED
  missing field `primary`, line: 84, column: 4

Scope note

Devin flagged that the other multi-valued structs (Email, PhoneNumber, Im, Photo, Entitlement, X509Certificate) keep a plain Option<bool> and would still reject a stringified "true". Left as-is deliberately, for two reasons:

• The missing-field bug only occurs where deserialize_with is present, since that is what suppresses serde's Option default. Role::primary is the only production use of deserialize_with in the crate, so there are no other latent instances. Plain Option<bool> fields already default to None when the key is absent.
• The leniency itself is targeted, not general. It arrived in 8d5cc19 alongside src/test_data/entra_user_creation_test.json (from Microsoft's SCIM validator), where Entra sends a real boolean for primary on emails and phoneNumbers and a string only on roles. Widening it elsewhere has no driving case today.

Release

• Cargo.toml 0.4.1 → 0.4.2 (Cargo.lock is gitignored, matching chore(release): bump crate version to 0.4.1 #42).
• CHANGELOG.md gains a 0.4.2 Fixed entry.

Tagging v0.4.2 after merge triggers publish + release.

Verification

cargo fmt --check, cargo clippy --all-targets -- -D warnings, and cargo test (137 unit + 37 doctests) all pass locally.

Original authorship is credited via Co-authored-by. #44 can be closed once this merges.