Nextcloud federation alias domain.

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Is your feature request related to a problem? Please describe.
I feel like nextcloud would feel like it's intergrated better when external users would share to an email address like format instead of to the nextcloud url. It would look more professional sharing a file to, or receiving a file from johndoe@organisation.tld instead of johndoe@cloud.organisation.tld, sometimes even longer. When sharing to a format which matches a user's exact email address it will be much clearer who you are interacting with.

Describe the solution you'd like
I was thinking about a solution where you would be able to configure a url on the target domain(s) that will execute a php script or perhaps a proxy passthrough to the nextcloud instance or global site selector targeting the federation endpoint. Then, administrators would be able to configure a domain for all users, per group or per user (I myself manage multiple domains so being able to for seperate groups would be awesome). For something where users are retrieved from ldap, maybe obtain the domain from their email address and check if the domain is set-up for federate sharing? Otherwise fallback to a default domain or to the domain lf the nextcloud instance.

Describe alternatives you've considered
Install nextcloud on my main domain and make proxy passthroughs for some urls that are needed to show the main website, though this is not the best nor an elegant option that will most likely not last forever.

Additional context
This in my opinion is one of the drawbacks that make nextcloud feel less professional. Within google workspace or microsoft 365 this makes much more sense. I feel like this functionality would intergrate nextcloud much better with organisations. Let me know what the rest of you all think about this. I'm excited to see how others are tackling this and excited to see possible alternatives to this!

Start by reviewing the existing federation-sharing flow and how LDAP users, groups, and domains are represented; the issue names no files, tests, or entry points. Before implementation, define the supported alias configuration scope and fallback behavior, then document the design and tests needed to verify federation addresses.