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

Cargo.lock

@@ -5515,6 +5515,7 @@ dependencies = [
  "scalar_api_reference",
  "sentry",
  "serde",
+ "serde-binhum",
  "serde_json",
  "serde_with",
  "sha1 0.10.6",
@@ -9379,6 +9380,16 @@ dependencies = [
  "serde_derive",
 ]
 
+[[package]]
+name = "serde-binhum"
+version = "0.1.0"
+dependencies = [
+ "darling 0.23.0",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.106",
+]
+
 [[package]]
 name = "serde-untagged"
 version = "0.1.9"
@@ -13443,12 +13454,13 @@ dependencies = [
  "chrono",
  "dashmap",
  "deadpool-redis",
+ "eyre",
  "futures",
  "lz4_flex",
+ "postcard",
  "prometheus",
  "redis",
  "serde",
- "serde_json",
  "thiserror 2.0.17",
  "tokio",
  "tracing",