Comprehensive documentation standards

Create clear, well-structured API documentation following these practices:

1. Use proper formatting:
   • Separate distinct thoughts with blank lines
   • Ensure consistent paragraph structure
   • Add proper spacing after section headers

/// Create a multipart form to be used in API responses.
///
/// This struct implements [`IntoResponse`], and so it can be returned from a handler.

1. Use correct references:
   • Place code elements in backticks with proper linking: [Type] not Type or Type
   • Use intra-doc links for internal references: [order-of-extractors]: crate::extract#the-order-of-extractors
   • Specify version requirements when applicable: “This macro is only available with Rust >= 1.80”
2. Write informative examples:
   • Implement documentation tests where possible: #[doc(test)]
   • Include complete, runnable code examples
   • Add explanatory comments for complex operations
   • Format examples consistently with proper spacing
3. Ensure completeness:
   • Document security implications of sensitive operations
   • Clarify parameter constraints and return value behaviors
   • Use precise language: “This allows sharing state with IntoResponse implementations” not “This allows sharing state with IntoResponse implementations”
   • Add trailing periods to documentation sentences

Documentation should be treated as a first-class feature - it’s often the first interaction users have with your API.