adding both a user and group to content requires two different functions

To add a user or group to content, two different functions are required Examples:

Add user:

content_add_user(content, user_guid, role = access_type)

Add a group:

content_add_group(content, group_guid, role = access_type)

A common use case may be to have a list of users and groups to add to content, however, the current implementation requires that list to be segregated by users and groups. A cleaner implementation would allow content_add_permission to take either a user or a group guid and then sort out internally what type of principal it is.

See https://github.com/posit-dev/connect-cookbook/pull/65 for how this requires two different recipes to do more or less the same thing.

Start by comparing content_add_user and content_add_group and reviewing the linked connect-cookbook pull request for the two existing recipes. Determine how content_add_permission can accept either a user or group GUID and identify the relevant tests or examples to update; done means one function supports mixed principals without requiring separate lists.