[services-lib] Add BlobInfo utility type

Summary:
Adds a type that represents the information of an owned blob. This is useful for storing the blob reference in DDB

Depends on D8777, D8790

Test Plan: Tested later with real usage.

Reviewers: michal, jon

Reviewed By: michal

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8791

services/comm-services-lib/src/blob/mod.rs

@@ -1,2 +1,3 @@
 #[cfg(feature = "blob-client")]
 pub mod client;
+pub mod types;

services/comm-services-lib/src/blob/types.rs

@@ -0,0 +1,54 @@
+use aws_sdk_dynamodb::types::AttributeValue;
+use derive_more::Constructor;
+use std::collections::HashMap;
+
+use crate::database::{AttributeTryInto, DBItemError, TryFromAttribute};
+
+const BLOB_HASH_DDB_MAP_KEY: &str = "blob_hash";
+const HOLDER_DDB_MAP_KEY: &str = "holder";
+
+/// Blob owning information - stores both blob_hash and holder
+#[derive(Clone, Debug, Constructor)]
+pub struct BlobInfo {
+  pub blob_hash: String,
+  pub holder: String,
+}
+
+impl From<BlobInfo> for AttributeValue {
+  fn from(value: BlobInfo) -> Self {
+    let map = HashMap::from([
+      (
+        BLOB_HASH_DDB_MAP_KEY.to_string(),
+        AttributeValue::S(value.blob_hash),
+      ),
+      (
+        HOLDER_DDB_MAP_KEY.to_string(),
+        AttributeValue::S(value.holder),
+      ),
+    ]);
+    AttributeValue::M(map)
+  }
+}
+impl From<&BlobInfo> for AttributeValue {
+  fn from(value: &BlobInfo) -> Self {
+    AttributeValue::from(value.to_owned())
+  }
+}
+
+impl TryFromAttribute for BlobInfo {
+  fn try_from_attr(
+    attribute_name: impl Into<String>,
+    attribute: Option<AttributeValue>,
+  ) -> Result<Self, DBItemError> {
+    let attr_name: String = attribute_name.into();
+    let mut inner_map: HashMap<String, AttributeValue> =
+      attribute.attr_try_into(&attr_name)?;
+    let blob_hash = inner_map
+      .remove("blob_hash")
+      .attr_try_into(format!("{attr_name}.blob_hash"))?;
+    let holder = inner_map
+      .remove("holder")
+      .attr_try_into(format!("{attr_name}.holder"))?;
+    Ok(BlobInfo { blob_hash, holder })
+  }
+}