Organizer ID can exceed maximum integer value on 32-bit installs

On 32-bit builds of PHP, numbers that exceed the limits of a 32-bit integer (±2,000,000,000) are silently cast to a `float`. The `organizer_id` expects an integer. For my account, those values were all greater than that maximum number (11 digits) and silently failed. Allowing the `organizer_id` to be passed in as a `string` avoids the issue.

Search the plugin for organizer_id handling and any integer validation or parameter documentation. Reproduce the issue with an 11-digit organizer ID on a 32-bit PHP install, then verify that the value is accepted as a string without silent conversion or failure.

Written by the indexing model from the issue text.