doc: Instructions unclear on how to fetch token from regional controller sunbeam deployment with MAAS provider

During multi-region deployment for sunbeam with MAAS, I have deployed regional controller site, now I need to deploy another secondary sunbeam site. As per documentation for during secondary cluster bootstrap, we need to pass the $token to connect to regional_controller site. However, there are no clear instructions on how to fetch a token from regional_controller sunbeam deployment.
```
Secondary regions will reside in separate Sunbeam deployments, using a region controller token to connect to the primary region.

$ sunbeam cluster bootstrap --region-controller-token=$token
$ sunbeam cluster deploy
```

But it does not describe how to get the token.

In the manual provider section, this command is used to fetch a token:
https://canonical-openstack.readthedocs-hosted.com/en/latest/how-to/misc/multiregion-deployments/#secondary-regions
```
In order to access the region controller, each secondary region node will need a token obtained from the region controllers:

sunbeam cluster add-secondary-region-node $fqdn
```

But this command is not available when using the maas provider.

---
Document: how-to/misc/multiregion-deployments.rst

Start with how-to/misc/multiregion-deployments.rst and its secondary-regions section. Compare the documented manual-provider command with the MAAS-provider workflow and determine how a token is obtained from the regional controller for secondary cluster bootstrap. Done means the documentation gives clear MAAS-specific token retrieval instructions.

Written by the indexing model from the issue text.