Add code challenge support

src/utils/crypt_utils.rs

@@ -0,0 +1,6 @@
+use digest::Digest;
+
+#[inline]
+pub fn sha256(input: &[u8]) -> Vec<u8> {
+    sha2::Sha256::digest(input).to_vec()
+}

src/utils/mod.rs

@@ -1,4 +1,5 @@
 pub mod err;
 pub mod time;
 pub mod network_utils;
-pub mod string_utils;
+pub mod string_utils;
+pub mod crypt_utils;