Introduce atrium_api::types::Unknown for unknown fields

Closes sugyan#204.

Author: str4d

atrium-api/CHANGELOG.md

@@ -6,6 +6,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- `atrium_api::types::Unknown`
+
+### Changed
+- `unknown` field types that don't have a well-known format now have the type
+  `atrium_api::types::Unknown` instead of `atrium_api::records::Record`.
+
 ## [0.23.2](https://github.com/sugyan/atrium/compare/atrium-api-v0.23.1...atrium-api-v0.23.2) - 2024-07-03
 
 ### Added

atrium-api/src/app/bsky/embed/record.rs

@@ -128,6 +128,8 @@ pub enum Union<T> {
     Unknown(UnknownData),
 }
 
+/// Data with an unknown schema in an open [`Union`].
+///
 /// The data of variants represented by a map and include a `$type` field indicating the variant type.
 #[derive(serde::Serialize, serde::Deserialize, Debug, Clone, PartialEq, Eq)]
 pub struct UnknownData {
@@ -137,6 +139,30 @@ pub struct UnknownData {
     pub data: Ipld,
 }
 
+/// Arbitrary data with no specific validation and no type-specific fields.
+///
+/// Corresponds to [the `unknown` field type].
+///
+/// [the `unknown` field type]: https://atproto.com/specs/lexicon#unknown
+#[derive(serde::Serialize, serde::Deserialize, Debug, Clone, PartialEq, Eq)]
+#[serde(try_from = "Ipld")]
+pub struct Unknown {
+    pub data: Ipld,
+}
+
+impl TryFrom<Ipld> for Unknown {
+    type Error = &'static str;
+
+    fn try_from(value: Ipld) -> Result<Self, Self::Error> {
+        // Enforce the ATProto data model.
+        // https://atproto.com/specs/data-model
+        match value {
+            Ipld::Float(_) => Err("Floats are not allowed in ATProto"),
+            data => Ok(Unknown { data }),
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

atrium-api/src/com/atproto/admin/defs.rs

@@ -566,8 +566,10 @@ fn unknown_type(unknown: &LexUnknown, name: Option<&str>) -> Result<(TokenStream
     let description = description(&unknown.description);
     if name == Some("didDoc") {
         Ok((description, quote!(crate::did_doc::DidDocument)))
-    } else {
+    } else if name == Some("record") {
         Ok((description, quote!(crate::records::Record)))
+    } else {
+        Ok((description, quote!(crate::types::Unknown)))
     }
 }