Start login OTP

curl --request POST \
  --url https://{appId}.session.prelude.dev/v1/session/login/otp \
  --header 'Content-Type: application/json' \
  --header 'X-App-Id: <x-app-id>' \
  --data '{
  "identifier": {
    "type": "phone_number",
    "value": "+306912345678"
  }
}'

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