Add warning field to fetch logs response.

The intention of adding this field is to handle moved repositories.
When a repository is moved, Warg will use the new repository name
instead, but the users must be alerted so they can update their
dependency list.

crates/api/src/v1/fetch.rs

@@ -52,6 +52,9 @@ pub struct FetchLogsResponse {
     /// The package records appended since last known package record ids.
     #[serde(default, skip_serializing_if = "IndexMap::is_empty")]
     pub packages: IndexMap<LogId, Vec<PublishedRecord>>,
+    /// An optional list of warnings.
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub warnings: Vec<FetchWarning>,
 }
 
 /// Represents a fetch package names request.
@@ -72,6 +75,13 @@ pub struct FetchPackageNamesResponse {
     pub packages: IndexMap<LogId, Option<PackageName>>,
 }
 
+/// A warning message.
+#[derive(Serialize, Deserialize, Debug)]
+pub struct FetchWarning {
+    /// The warning message itself
+    pub message: String,
+}
+
 /// Represents a fetch API error.
 #[non_exhaustive]
 #[derive(Debug, Error)]

crates/client/src/lib.rs

@@ -629,6 +629,11 @@ impl<R: RegistryStorage, C: ContentStorage, N: NamespaceMapStorage> Client<R, C,
                     packages: Cow::Borrowed(&last_known),
                 })
                 .await
+                .inspect(|res| {
+                    for warning in res.warnings.iter() {
+                        tracing::warn!("WARNING: {}", warning.message);
+                    }
+                })
                 .map_err(|e| {
                     ClientError::translate_log_not_found(e, |id| {
                         packages.get(id).map(|p| p.name.clone())

crates/server/openapi.yaml

@@ -808,6 +808,12 @@ components:
           maxItems: 1000
           items:
             $ref: "#/components/schemas/PublishedRecordEnvelope"
+        warnings:
+          type: array
+          description: An optional list of warnings.
+          maxItems: 1000
+          items:
+            $ref: "#/components/schemas/FetchWarning"
         packages:
           type: object
           description: The map of package log identifier to package records.
@@ -1085,6 +1091,12 @@ components:
               maxLength: 1048576
               example: "ZXhhbXBsZQ=="
         - $ref: "#/components/schemas/Signature"
+    FetchWarning:
+      description: A warning message
+      properties:
+        message:
+          description: The warning message itself.
+          type: string 
     PublishedRecordEnvelope:
       description: A signed envelope body with the published registry log index.
       allOf:

crates/server/src/api/v1/fetch.rs

@@ -160,6 +160,7 @@ async fn fetch_logs(
         more,
         operator,
         packages: map,
+        warnings: Vec::default(),
     }))
 }