user_reference_invite makes user.mail invalid by adding required mail schema keys without default config

Problem/Motivation

After enabling user_reference_invite, drush config:inspect reports validation errors for user.mail. The module alters the core user.mail config schema and adds three invitation mail mappings, but it does not add matching default values to user.mail during install. As a result, the schema expects required keys that are missing from the active user.mail config.

drush config:inspect --detail --only-error --format=json reports below errors:

{
    "user.mail": {
        "key": "user.mail",
        "status": "Correct",
        "validatability": "100%",
        "data": "3 errors"
    },
    "user.mail:": {
        "key": " user.mail:",
        "status": "Correct",
        "validatability": "Validatable",
        "data": [
            "'user_invitation' is a required key.",
            "'user_invitation_reminder' is a required key.",
            "'user_invitation_batch_complete' is a required key."
        ]
    }
}

When using the default table formatter, Drush/config_inspector may also fail to
render the output because the validation messages are returned as an array:

Array to string conversion CalculateWidths.php:83
A cell must be a TableCell, a scalar or an object implementing "__toString()", "array" given.

Steps to reproduce

1. Install Drupal 11.
2. Install and enable User Reference with Invite 1.4.0: drush en -y user_reference_invite
3. Run: drush config:inspect --detail --only-error --format=json

Proposed resolution

Ensure the schema and installed config agree.