refactor: use dtos in controllers

backend/internal/common/errors.go

@@ -13,6 +13,7 @@ var (
 	ErrOidcMissingClientCredentials = errors.New("client id or secret not provided")
 	ErrOidcClientSecretInvalid      = errors.New("invalid client secret")
 	ErrOidcInvalidAuthorizationCode = errors.New("invalid authorization code")
+	ErrOidcInvalidCallbackURL       = errors.New("invalid callback URL")
 	ErrFileTypeNotSupported         = errors.New("file type not supported")
 	ErrInvalidCredentials           = errors.New("no user found with provided credentials")
 )