## About the changes
Implements custom root roles, encompassing a lot of different areas of
the project, and slightly refactoring the current roles logic. It
includes quite a clean up.
This feature itself is behind a flag: `customRootRoles`
This feature covers root roles in:
- Users;
- Service Accounts;
- Groups;
Apologies in advance. I may have gotten a bit carried away 🙈
### Roles
We now have a new admin tab called "Roles" where we can see all root
roles and manage custom ones. We are not allowed to edit or remove
*predefined* roles.

This meant slightly pushing away the existing roles to `project-roles`
instead. One idea we want to explore in the future is to unify both
types of roles in the UI instead of having 2 separate tabs. This
includes modernizing project roles to fit more into our current design
and decisions.
Hovering the permissions cell expands detailed information about the
role:

### Create and edit role
Here's how the role form looks like (create / edit):

Here I categorized permissions so it's easier to visualize and manage
from a UX perspective.
I'm using the same endpoint as before. I tried to unify the logic and
get rid of the `projectRole` specific hooks. What distinguishes custom
root roles from custom project roles is the extra `root-custom` type we
see on the payload. By default we assume `custom` (custom project role)
instead, which should help in terms of backwards compatibility.
### Delete role
When we delete a custom role we try to help the end user make an
informed decision by listing all the entities which currently use this
custom root role:

~~As mentioned in the screenshot, when deleting a custom role, we demote
all entities associated with it to the predefined `Viewer` role.~~
**EDIT**: Apparently we currently block this from the API
(access-service deleteRole) with a message:

What should the correct behavior be?
### Role selector
I added a new easy-to-use role selector component that is present in:
- Users

- Service Accounts

- Groups

### Role description
I also added a new role description component that you can see below the
dropdown in the selector component, but it's also used to better
describe each role in the respective tables:

I'm not listing all the permissions of predefined roles. Those simply
show the description in the tooltip:

### Role badge
Groups is a bit different, since it uses a list of cards, so I added yet
another component - Role badge:

I'm using this same component on the profile tab:

## Discussion points
- Are we being defensive enough with the use of the flag? Should we
cover more?
- Are we breaking backwards compatibility in any way?
- What should we do when removing a role? Block or demote?
- Maybe some existing permission-related issues will surface with this
change: Are we being specific enough with our permissions? A lot of
places are simply checking for `ADMIN`;
- We may want to get rid of the API roles coupling we have with the
users and SAs and instead use the new hooks (e.g. `useRoles`)
explicitly;
- We should update the docs;
- Maybe we could allow the user to add a custom role directly from the
role selector component;
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Co-authored-by: Gastón Fournier <gaston@getunleash.io>