Invalid characters allowed in mobileNumber Field of /notifications/api/v1/orders Endpoint

[Ahmed-Ghanam]

Description

The POST /notifications/api/v1/orders endpoint does not properly handle invalid characters in the mobileNumber field. For example, submitting a value like "+47invalidChar" results in an internal server error (500) without providing a meaningful error message to the user.

Steps to Reproduce

1. Send a POST request to the /notifications/api/v1/orders endpoint with a mobileNumber field containing invalid characters (e.g., "+47invalidChar").
2. Observe that the API responds with an internal server error (500) instead of rejecting the request with a meaningful validation error message.

Example Request:

{
    "notificationChannel": "Sms",
    "smsTemplate": {
        "senderNumber": "+4746269164",
        "body": "Hei, Du har en ny melding i Altinn."
    },
    "sendersReference": "907c8054-b2cc-4dca-b4df-c95b89860762",
    "recipients": [
        {
            "mobileNumber": "+47invalidChar"
        }
    ]
}

Expected Behavior

The API should validate the mobileNumber field to ensure it adheres to valid international phone number format standards. If invalid characters are submitted, the API should reject the request with a descriptive error message, such as "Invalid mobile number format," preventing further processing.

Suggested Fix

Introduce or improve input validation on the mobileNumber field to ensure it only accepts valid numeric characters following international phone number standards. When validation fails, return a clear and informative error message, rejecting the request before it reaches internal processing.

Acceptance criteria:

• Validation-scheme documented at docs.altinn.studio
• Failed validations give response-code 400 and a message (e.g. "mobileNumber format not adhering to...")

[olebhansen]

Updating issue to be "adhere to validation standard + document this", to avoid confusion on permitted content. Feiled validations should give 400 and a sensible message.

See: https://altinn.slack.com/archives/C069J71UQCQ/p1727789663181299?thread_ts=1727703986.978639&cid=C069J71UQCQ

Skjønner, siste klarering da: Jeg får 400 bad request på visse telefonnumre og formater, kan du si hvilken standard dere bruker for å validere gyldige numre?
Ut ifra testingen min så virker det til å være E.164

[hggutvik]

Our initial guess was correct - the 500 error results from the validation package not handling the letters

[SandGrainOne]

Manual tests performed and changes approved.