Function normalize 

pub fn normalize(sql: &str) -> String

Normalize a SQL string for use as a cache key.

Applies:

• Collapse any sequence of whitespace (spaces, tabs, newlines) to a single ASCII space.
• Trim leading and trailing whitespace.
• Uppercase all characters outside of string literals (so select and SELECT produce the same key).

This is a lightweight lexical normalization, not a full AST round-trip. It is suitable for prepared-statement cache key generation but does not guarantee two semantically identical queries will produce the same key (e.g. different identifier quoting styles will still differ).

Example

use oxisql_parse::normalize;
assert_eq!(normalize("select  id  from  users"), "SELECT ID FROM USERS");