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/models/exp/project.rs

@@ -54,7 +54,7 @@ macro_rules! define_project_components {
         pub struct ProjectSerial {
             $(
                 #[validate(nested)]
-                #[serde(default, skip_serializing_if = "Option::is_none")]
+                #[serde(default)]
                 pub $field_name: Option<$ty>,
             )*
         }
@@ -114,7 +114,6 @@ macro_rules! define_project_components {
         #[derive(Debug, Clone, Default, Serialize, Deserialize, utoipa::ToSchema)]
         pub struct ProjectQuery {
             $(
-                #[serde(skip_serializing_if = "Option::is_none")]
                 pub $field_name: Option<Query<$ty>>,
             )*
         }