rename membership and adopt newtype pattern

[stefan0xC]

I've been working on improving Vaultwarden's legibility by renaming the UsersOrganizations to simply Membership and making it clearer when something is referring to the User and when to a Membership relation.

After doing that I was motivated to try my hands on using the newtype pattern so that the Rust type system can be used to check on compile time if we always call the right uuid because there are a lot of Strings that can be used interchangeably otherwise.

For example I noticed that we are passing the wrong id here:

vaultwarden/src/api/core/organizations.rs

Line 910 in ed4ad67

let mut group_entry = GroupUser::new(String::from(group), user.uuid.clone());

Because in contrast to CollectionUser the GroupUser::new actually expects a different id:

vaultwarden/src/db/models/group.rs

Line 122 in ed4ad67

pub fn new(groups_uuid: String, users_organizations_uuid: String) -> Self {

This was probably overlooked because it's not a major issue when a user is not correctly invited to a group and it only shows up as a small warning in the logs:

[2024-12-22 21:23:47.022][request][INFO] POST /api/organizations/152bd996-19f9-40ee-b991-e52333a7e719/users/invite
[2024-12-22 21:23:47.031][vaultwarden::db::models::group][WARN] User could not be found!
[2024-12-22 21:23:48.082][response][INFO] (send_invite) POST /api/organizations/<org_id>/users/invite => 200 OK