Refactor codebase

internal/interfaces/error_message.go

@@ -0,0 +1,20 @@
+// Package interfaces defines the core interfaces and shared structures for the CLI Proxy API server.
+// These interfaces provide a common contract for different components of the application,
+// such as AI service clients, API handlers, and data models.
+package interfaces
+
+import "net/http"
+
+// ErrorMessage encapsulates an error with an associated HTTP status code.
+// This structure is used to provide detailed error information including
+// both the HTTP status and the underlying error.
+type ErrorMessage struct {
+	// StatusCode is the HTTP status code returned by the API.
+	StatusCode int
+
+	// Error is the underlying error that occurred.
+	Error error
+
+	// Addon contains additional headers to be added to the response.
+	Addon http.Header
+}