Add groups enrollment logic to be applied after users registration

[garaimanoj]

Properties to be added in application.yml

iam:
  registration:
    default-groups:
      - name: /atlas
        enrollment: INSERT
      - name: /privileged
        enrollment: GROUP_REQUEST

When setting up new user accounts, administrators often need to determine which group these accounts should belong to by default. Here’s what you need to know:

name (Default Group):

• The term “name” represents the specific group that serves as the default destination for new accounts.

• When a user account is created, it automatically becomes a member of this default group unless specified otherwise.

enrollment Types:

There are two enrollment types that determine how new accounts join the default group:

• INSERT Enrollment: With this type, the system swiftly adds the new account to the default group during account creation.
  No additional steps or user interaction are required—the account slips seamlessly into the group.

• GROUP_REQUEST Enrollment (Not implemented): Here, the process is a bit more interactive. New request to join the group will be sent to the admin.

Current Functionality:
As of now, the system has implemented the INSERT enrollment type.
When creating a new account, it automatically becomes part of the default group (“name”) if that group exists.

[enricovianello]

The main changement is related to addind a DefaultGroup properties class, such as all the others already defined into IamProperties

[enricovianello]

Just a minor cosmetic fix requested. Another thing we could add to this PR description the example of the application.yml configuration required (e.g. the part we removed).
This will make easier to understand it when reading new features from release notes.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
96.2% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud