Pass credentials via RDP

### Describe the Bug

@AstralDestiny

Creating issue as requested by Astral for the ability to pass RDP credentials without having to re-enter them all the time, either based of a user or a role.

### Environment

- OS Type & Version:
- Pangolin Version:
- Edition (Community or Enterprise):
- Gerbil Version:
- Traefik Version:
- Newt Version:
- Client Version:

### To Reproduce

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### Expected Behavior

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No files, tests, or entry points are identified in the issue. Clarify how RDP credentials should be supplied, whether behavior is based on a user or role, and what security constraints apply; done should mean users can access RDP without repeatedly re-entering credentials.

Written by the indexing model from the issue text.