Add include_hidden parameter to Spond.get_events()

[Yannis-G]

Description

This PR enhances the functionality of Spond.get_events() by adding a new parameter, include_hidden, which allows fetching hidden events that are visible to users with at least admin permissions, addressing the feature request in issue #164.

Note: The include_hidden parameter is only supported if a group_id is provided. If used without group_id, the Spond API will respond with an error:

'includeHidden' filter is only available inside a group

Therefore, this parameter is included in the request only when both group_id and include_hidden=True are specified. Otherwise, the method behaves as it did previously.

Summary of Changes

• New Parameter: Added include_hidden to the method signature.
• Update Docstring: Tried to match the current style of the docstring.
• API Parameter: The "includeHidden" flag is added to the request parameters only if both group_id is provided and include_hidden is set to True. The behavior remains unchanged if these conditions are not met.

Example Usage

events = await spond_client.get_events(group_id=<GROUP_ID>, include_hidden=True)

[elliot-100]

Hi - many thanks for this. I'll have a go at testing it against live data. Might take a few weeks.