RDP-specific Coder Desktop deep link

[ThomasK33]

Add RDP-specific logic into Coder Desktop so that all coder apps marked with external=true and a URL matching to coder:/v0/open/agent/<agent ID>/rdp?username=<username>&password=<passwpord> will be rendered as buttons and have RDP-specific logic in place. This logic can include fetching additional information or credentials in Coder Desktop and creating an .rdp file or comparable integrations.

[spikecurtis]

Thinking about this a bit more, I think the URI format should be:

coder://coder.example.com/v0/open/ws/<workspace-name>/agent/<agent-name>/rdp?username=<username>&password=<password>

We should include the authority, so that if you have multiple Coder deployments and you click a link from one of them, and Coder Desktop is signed into a different one, the you can get a sensible error.

We should prefer name references over UUIDs, so that it's possible to bookmark. If we used Agent UUIDs, the link would break as soon as we rebuild.

[matifali]

We should include the authority, so that if you have multiple Coder deployments and you click a link from one of them, and Coder Desktop is signed into a different one, the you can get a sensible error.

This is a good addition. It would help provide better self-troubleshooting.