feat: add latestSchema query for retrieving schema updates

Implements the `latestSchema` query to fetch the latest schema 
updates for an organization. This change enhances the GraphQL API by
allowing clients to retrieve the most recent schema version and its 
associated subgraphs. The resolver performs necessary access checks, 
logs relevant information, and generates the Cosmo router configuration 
from fetched subgraph SDLs, returning structured schema update details.

graph/schema.resolvers.go

@@ -238,6 +238,72 @@ func (r *queryResolver) Supergraph(ctx context.Context, ref string, isAfter *str
 	}, nil
 }
 
+// LatestSchema is the resolver for the latestSchema field.
+func (r *queryResolver) LatestSchema(ctx context.Context, ref string) (*model.SchemaUpdate, error) {
+	orgId := middleware.OrganizationFromContext(ctx)
+
+	r.Logger.Info("LatestSchema query",
+		"ref", ref,
+		"orgId", orgId,
+	)
+
+	_, err := r.apiKeyCanAccessRef(ctx, ref, false)
+	if err != nil {
+		r.Logger.Error("API key cannot access ref", "error", err, "ref", ref)
+		return nil, err
+	}
+
+	// Get current services and schema
+	services, lastUpdate := r.Cache.Services(orgId, ref, "")
+	r.Logger.Info("Fetching latest schema",
+		"ref", ref,
+		"orgId", orgId,
+		"lastUpdate", lastUpdate,
+		"servicesCount", len(services),
+	)
+
+	subGraphs := make([]*model.SubGraph, len(services))
+	for i, id := range services {
+		sg, err := r.fetchSubGraph(ctx, id)
+		if err != nil {
+			r.Logger.Error("fetch subgraph", "error", err, "id", id)
+			return nil, err
+		}
+		subGraphs[i] = &model.SubGraph{
+			ID:        sg.ID.String(),
+			Service:   sg.Service,
+			URL:       sg.Url,
+			WsURL:     sg.WSUrl,
+			Sdl:       sg.Sdl,
+			ChangedBy: sg.ChangedBy,
+			ChangedAt: sg.ChangedAt,
+		}
+	}
+
+	// Generate Cosmo router config
+	cosmoConfig, err := GenerateCosmoRouterConfig(subGraphs)
+	if err != nil {
+		r.Logger.Error("generate cosmo config", "error", err)
+		cosmoConfig = "" // Return empty if generation fails
+	}
+
+	update := &model.SchemaUpdate{
+		Ref:               ref,
+		ID:                lastUpdate,
+		SubGraphs:         subGraphs,
+		CosmoRouterConfig: &cosmoConfig,
+	}
+
+	r.Logger.Info("Latest schema fetched",
+		"ref", update.Ref,
+		"id", update.ID,
+		"subGraphsCount", len(update.SubGraphs),
+		"cosmoConfigLength", len(cosmoConfig),
+	)
+
+	return update, nil
+}
+
 // SchemaUpdates is the resolver for the schemaUpdates field.
 func (r *subscriptionResolver) SchemaUpdates(ctx context.Context, ref string) (<-chan *model.SchemaUpdate, error) {
 	orgId := middleware.OrganizationFromContext(ctx)