feat(api): return cas-backend info

app/controlplane/api/controlplane/v1/cas_credentials.proto

@@ -1,5 +1,5 @@
 //
-// Copyright 2023 The Chainloop Authors.
+// Copyright 2023-2025 The Chainloop Authors.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -17,29 +17,37 @@ syntax = "proto3";
 
 package controlplane.v1;
 
-option go_package = "github.com/chainloop-dev/chainloop/app/controlplane/api/controlplane/v1;v1";
 import "buf/validate/validate.proto";
+import "controlplane/v1/response_messages.proto";
+
+option go_package = "github.com/chainloop-dev/chainloop/app/controlplane/api/controlplane/v1;v1";
 
 service CASCredentialsService {
-	rpc Get (CASCredentialsServiceGetRequest) returns (CASCredentialsServiceGetResponse);
+  rpc Get(CASCredentialsServiceGetRequest) returns (CASCredentialsServiceGetResponse);
 }
 
 message CASCredentialsServiceGetRequest {
-  Role role = 1 [(buf.validate.field).enum = {in: [1,2]}];
+  Role role = 1 [(buf.validate.field).enum = {
+    in: [
+      1,
+      2
+    ]
+  }];
   // during the download we need the digest to find the proper cas backend
   string digest = 2;
 
   enum Role {
-      ROLE_UNSPECIFIED = 0;
-      ROLE_DOWNLOADER = 1;
-      ROLE_UPLOADER = 2;
-  } 
+    ROLE_UNSPECIFIED = 0;
+    ROLE_DOWNLOADER = 1;
+    ROLE_UPLOADER = 2;
+  }
 }
 
 message CASCredentialsServiceGetResponse {
   Result result = 1;
-  
+
   message Result {
     string token = 2;
+    CASBackendItem backend = 3;
   }
-}
+}

app/controlplane/internal/service/cascredential.go

@@ -128,6 +128,6 @@ func (s *CASCredentialsService) Get(ctx context.Context, req *pb.CASCredentialsS
 	}
 
 	return &pb.CASCredentialsServiceGetResponse{
-		Result: &pb.CASCredentialsServiceGetResponse_Result{Token: t},
+		Result: &pb.CASCredentialsServiceGetResponse_Result{Token: t, Backend: bizCASBackendToPb(backend)},
 	}, nil
 }