identifiers: Add random ClientSecret generator

Requires the rand feature.

crates/ruma-identifiers/CHANGELOG.md

@@ -7,6 +7,7 @@ Breaking changes:
 Improvements:
 
 * Add `MatrixUri` to build `matrix:` URIs
+* Add `ClientSecret::new()` with the `rand` feature to generate a random client secret
 
 # 0.21.0
 

crates/ruma-identifiers/src/client_secret.rs

@@ -4,10 +4,26 @@
 ///
 /// Client secrets in Matrix are opaque character sequences of `[0-9a-zA-Z.=_-]`. Their length must
 /// must not exceed 255 characters.
+///
+/// You can create one from a string (using `ClientSecret::parse()`) but the recommended way is to
+/// use `ClientSecret::new()` to generate a random one. If that function is not available for you,
+/// you need to activate this crate's `rand` Cargo feature.
 #[repr(transparent)]
 #[derive(PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct ClientSecret(str);
 
+impl ClientSecret {
+    /// Creates a random client secret.
+    ///
+    /// This will currently be a UUID without hyphens, but no guarantees are made about the
+    /// structure of client secrets generated from this function.
+    #[cfg(feature = "rand")]
+    pub fn new() -> Box<Self> {
+        let id = uuid::Uuid::new_v4();
+        Self::from_owned(id.to_simple().to_string().into_boxed_str())
+    }
+}
+
 opaque_identifier_validated!(ClientSecret, ruma_identifiers_validation::client_secret::validate);
 
 #[cfg(test)]