Defines the structure of an event type in the system. This schema determines how events are interpreted, validated, and stored.
Root structure:

• The schema is an object with a mandatory property fields.
• fields is an object where each key represents the name of an event field.

Field definition:

• Each field object defines:
  • type: the data type of the field. Allowed values: "string", "numeric", "boolean", "datetime".
  • required: a boolean indicating whether the field is mandatory in the event payload.
• No additional properties are allowed within each field definition.
• At least one field must be defined.

Important notes:

• Any update to this schema will overwrite the existing definition in the database.
• Changes may affect event processing, calculations, and integrations.
• After modifying the schema, verify that all fields in your field definitions
  referencing this event type (sourceEventField) still exist and are compatible
  with their corresponding sourceEventType.
• Carefully review and test changes before applying them in production.

Example:

  "fields": {
    "email": {
      "type": "string",
      "required": true
    },
    "age": {
      "type": "numeric",
      "required": false
    },
    "signupDate": {
      "type": "datetime",
      "required": true
    }
  }
}