Fix some clippy warnings

src/data.rs

@@ -146,7 +146,7 @@ fn validate_email(email: &str) -> Result<(), RegistrationError> {
     Regex::new(r"^[^@\s]+@[^@\s]+\.[^@\s]+$")
         .unwrap()
         .is_match(email)
-        .then(|| ())
+        .then_some(())
         .ok_or(RegistrationError::InvalidEmail)
 }
 

src/filters.rs

@@ -45,5 +45,5 @@ pub fn linebreaksbr(value: &Value, _: &HashMap<String, Value>) -> tera::Result<V
     } else {
         return Err("The linebreaksbr filter can only be applied to strings".into());
     };
-    Ok(Value::String(text.replace("\r\n", "<br>").replace("\n", "<br>")))
+    Ok(Value::String(text.replace("\r\n", "<br>").replace('\n', "<br>")))
 }

src/main.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::needless_borrow)]
+
 #[macro_use]
 extern crate diesel;
 extern crate diesel_migrations;