Manages large cookies by splitting them into multiple set-cookie headers (chunks) and reassembling them on read. Uses a 'chunks:N' marker format and handles chunk removal. This is a self-contained utility that could be extracted into any HTTP-based project to handle cookie size limits, demonstrating careful state management and backward compatibility.

Implements `ISecureDataFormat<AuthenticationTicket>` for creating and validating JWT tokens. Uses `JwtSecurityTokenHandler` with issuer, audience, and signing key validation. It is decoupled from the OWIN environment and could be reused in any .NET Framework project needing JWT token handling. The code is cleanly separated and configurable via `TokenValidationParameters`.

Implements `IFileSystem` to provide file and directory enumeration on the physical disk. Maps root path and enumerates subdirectories and files. This is a simple, isolated adapter that could be reused in any file-serving middleware or tool. It demonstrates good separation of concerns by abstracting file system operations.

Static utility class for parsing HTTP Range headers (`Range: bytes=...`) and normalizing range units. Handles multiple ranges and unit parsing. This is a self-contained piece of logic that could be extracted into any HTTP library, showcasing careful compliance with RFC 7233 and edge case handling.

Core implementation of `IAppBuilder` that manages middleware registration and pipeline construction. Supports adding middleware by delegate, type, or instance, and provides signature conversion (adapting different delegate shapes). This is a foundational pattern for building composable middleware pipelines, and while it is tightly integrated with OWIN, the concept and implementation of a linear middleware builder is a reusable architectural pattern.