Derive Macro Iterable 

#[derive(Iterable)]

Derives IntoIterator implementations and iterator methods for single-field tuple structs.

Generates three IntoIterator implementations:

• Owned: for item in config
• Borrowed: for item in &config
• Mutable: for item in &mut config

Also generates convenience methods:

• iter() - returns an iterator over immutable references
• iter_mut() - returns an iterator over mutable references

Requirements

• Must be a tuple struct with exactly one field
• The field must implement IntoIterator
• For iter() and iter_mut(), the field should have these methods (like HashMap, Vec, etc.)