feat: Resources for groups and memberships

[JonasBak]

Describe the feature request

I would like to be able to create and manage unleash groups and group memberships using terraform.

Background

Today we assign users to projects directly using unleash_project_access, but we're currently reworking the way we assign permissions/access to different systems.
We would like to be able to create a group for each team in the workspace where we manage teams (across different systems), and then look up that team from the workspace where we set up "projects" (across different systems) and grant that team access to the unleash projects they "own".
We're currently not able to achieve this, as there aren't resources to manage groups in unleash.

A workaround would be to output team-members from the "teams workspace" and read that from the "projects workspace", and assign users directly to each project, but I'd prefer to keep the way we manage access similar across the different services we use.

Solution suggestions

Implement unleash_group resource and data source. Membership could either be managed directly on the unleash_group resource, or using a separate resource. My preference would be using a separate resource, and that seems common among other providers as well.

I could look into implementing this myself, but it seems like the unleash-server-api-go library doesn't support groups api.

[ivarconr]

Thanks @JonasBak, this makes sense. We have added to the backlog for the terraform provider.