feat: implemented service/transport/main layers

internal/pkg/errcodes/errcodes.go

@@ -0,0 +1,25 @@
+package errcodes
+
+import (
+	"strings"
+)
+
+type ErrorCode struct {
+	StatusCode int
+	Message    string
+	Details    string
+}
+
+var errorCodeCounter int32
+
+func New(statusCode int, message string, details ...string) *ErrorCode {
+	return &ErrorCode{
+		StatusCode: statusCode,
+		Message:    message,
+		Details:    strings.Join(details, " "),
+	}
+}
+
+func (e *ErrorCode) Error() string {
+	return e.Message
+}