feat: use postcard for redis serde (#6956)

* redo error handling in xredis

* give proper types to metadata fields

* add round-trip tests

* inline loader enum metadata fields

* postcard roundtrips

* prepare

* bump redis key version

* serde-binhum

* clippy

* fix

* fix frontend checking existence of component fields rather than non-null-ness

* prepare

apps/labrinth/src/auth/mod.rs

@@ -59,12 +59,6 @@ pub enum AuthenticationError {
     Url,
 }
 
-impl From<xredis::Error> for AuthenticationError {
-    fn from(error: xredis::Error) -> Self {
-        Self::Database(error.into())
-    }
-}
-
 impl actix_web::ResponseError for AuthenticationError {
     fn status_code(&self) -> StatusCode {
         match self {