Improvements to the participant group feature

Is your feature request related to a problem? Please describe.
The participant group feature is great for use cases where multiple people want to represent a certain group/entity with their participation actions. But managing these groups can feel overwhelming and complex for many people.

Describe the solution you'd like
In order to make group administration easier, there are several features we can implement to make it easier to administer these groups:

1. Allow creating user groups directly from the admin panel
2. Allow creating user groups without an email (+ what is that email used for today?)
3. Allow adding users to the groups instantly without an invitation/request to join process (only as an admin feature through the admin panel)
4. Allow adding users through autocomplete search of user's name or directly using the email associated with the user's email address
5. Allow hiding user's membership in the group, in case they wish not to be disclosed as a public member of that group (e.g. assistants)

Describe alternatives you've considered
We are currently helping the cities to use this feature and taking care of adding new members to the groups as it feels overwhelming and complex to do by themselves.

Additional context
We generally use this feature for the city employees to represent the city when they are posting ideas to the platform.

Many people don't even understand what the groups are and they mentally associate the extra features the group membership brings to them to having an administration access to the platform. This would also mentally make it easier for them to understand the groups in case management of the groups was also in the admin panel where they perform other admin tasks.

Does this issue could impact on users private data?
Adding group members through user search can expose platform users names/nicknames to the user but we already have this feature available in many other places and even for the participants e.g. when starting new conversations. This data is also available through the public API.

Adding users to the groups using their email might make email phishing possible but in case this feature is limited only for the admin users, it does not cause any extra impact on privacy as the emails are already available for admins through the participant search.

Funded by
Not funded right now, just writing this down to have it in the backlog