This issue tracks adding more concrete usage examples and additional tests to help users understand all the ways to specify partition keys with the impl Into<PartitionKey> API pattern.

• Add new tests to partition_key.rs demonstrating how to specify partition keys using various types (e.g., &str, String, () for empty, Vec types, etc) and validate these code paths work as intended.
• Update relevant doc comments in both the SDK API surface and models to include these usage patterns for developers as reference.
• Ensure documentation links to or references the new exhaustive tests so users can find working code examples easily.

Goal: Bring confidence that users can specify partition keys in all supported ways and improve discoverability with robust examples and test coverage.