9

### Bugs
- No significant bugs found in the visible portion of the code.

### Optimizations
- Simplify the Codable conformance by making `AttachedImage` conform directly to `Codable` instead of using a nested struct for encoding/decoding.
- Consider using `URL` type instead of `String` for the `url` property for better type safety and validation.

### Good points
- Adheres to Swift's best practices with the use of `public` access control.
- Smart use of `Hashable` and `Sendable` protocols suggesting immutability and safety in concurrent programming contexts.
- Clear and straightforward initialization method.

### Summary
The `AttachedImage` struct is well-designed with a focus on thread safety and immutability, as indicated by its conformance to `Sendable` and `Hashable`. The code is clean and concise, with only minor suggestions for improvement mainly around potential simplification and improved type safety. 

### Open source alternatives
- **Kingfisher**: A powerful, pure-Swift library for downloading and caching images from the web.
- **SDWebImage**: An asynchronous image downloader with cache support as a UIImageView category.