Add dotenvy to dev-dependencies and call dotenvy::dotenv().ok() in
the integration test common module and all examples so env vars can
be loaded from a .env file.
Add 91 integration tests (all #[ignore]) mirroring the JavaScript SDK's
integration test suite. Tests cover all endpoints: ping, apps, fields,
records, files, lists, and reports with success, auth, access, and
not-found scenarios.
Add 7 runnable examples (cargo run --example <name>) for quick manual
smoke testing against a real Onspring instance.
Both use env vars (API_BASE_URL, SANDBOX_API_KEY, TEST_*) matching the
JavaScript SDK setup.
Also rename crate to onspring-api-sdk-rust with [lib] name = "onspring"
so imports remain `use onspring::*`.
Stevan Freeborn