minify_sql removes spaces around symbols inside string literals

[yeizero]

Description
When using sql_minifier version 0.1.5, minify_sql incorrectly removes spaces around symbols inside string literals. This leads to incorrect SQL when the string content contains operators like > or <.

To Reproduce

use sql_minifier::minify_sql;

#[test]
fn test_string_with_symbols() {
    let sql = r#"
        INSERT INTO messages (content) VALUES ('A > B and C < D');
    "#;

    let minified = minify_sql(sql);
    assert_eq!(
        minified,
        "INSERT INTO messages(content) VALUES('A > B and C < D')"
    );
}

Expected behavior
The minified SQL should preserve all spaces and symbols inside string literals:

INSERT INTO messages(content) VALUES('A > B and C < D')

Actual behavior
Currently, minify_sql may remove spaces around > and < inside the string, breaking the SQL logic.

Environment

• sql_minifier version: 0.1.5
• Rust version: rustc 1.89.0 (29483883e 2025-08-04) cargo 1.89.0 (c24e10642 2025-06-23)
• OS: Microsoft Windows 11