Update an account holder

Updates the `accountHolderDetails` and `processingTier` of an account holder, and adds bank accounts and shareholders. When updating `accountHolderDetails`, parameters that are not included in the request are left unchanged except for the following object: * `metadata`: Updating the metadata replaces the entire object. This means that to update an existing key-value pair, you must provide the changes, as well as other existing key-value pairs. When updating any field in the following objec...