Function increment 

pub fn increment(key: &str, delta: i64) -> Result<i64>

Atomically increment a numeric value

If the key doesn’t exist, creates it with delta as the initial value. Uses compare-and-swap internally with automatic retries.

Arguments

• key - The key to increment
• delta - The amount to add (can be negative)

Returns

• Ok(new_value) - The new value after increment
• Err(StorageError) - Storage operation failed or value is not a valid i64

Example

// Increment a counter
let new_count = storage::increment("page_views", 1)?;
println!("Page views: {}", new_count);

// Decrement (using negative delta)
let remaining = storage::increment("credits", -10)?;
println!("Remaining credits: {}", remaining);