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

packages/serde-binhum/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "serde-binhum"
+version = "0.1.0"
+edition.workspace = true
+rust-version.workspace = true
+repository.workspace = true
+
+[lib]
+proc-macro = true
+
+[dependencies]
+darling = { workspace = true }
+proc-macro2 = { workspace = true }
+quote = { workspace = true }
+syn = { workspace = true, features = ["full"] }
+
+[lints]
+workspace = true