Adds support for default first broker login flow on realm level

[maximilian-krauss]

What this PR does / why we need it:

This PR adds support for a custom default first broker login flow defined on realm level:

realm: myRealm
firstBrokerLoginFlow: 'my-first-broker-login'
# ...

authenticationFlows:
- alias: my-first-broker-login
        providerId: basic-flow
        topLevel: true
        builtIn: false
        authenticationExecutions:
          - authenticatorFlow: true
            requirement: REQUIRED
            priority: 20
            autheticatorFlow: true
            flowAlias: my-first-broker-login User creation or linking
            userSetupAllowed: false
# ...

Without these changes the CLI was not able to import/update the firstBrokerLoginFlow because it was missing the special treatment like browserFlow or registrationFlow.

Special notes for your reviewer:

Have a nice day 🙂

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

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

See analysis details on SonarQube Cloud