[Feature Request] Allow setting remote related WI relations

[asmundg]

Is your feature request related to a problem? Please describe.
az boards work-item relation add has a hard requirement on the added relation being a link to a local work item that can be looked up by id. This means that it's impossible to add a relation to a remote related work item, since this does not have a local work item id that can be looked up.

Describe the solution you'd like
It should be possible to add a remote related work item relation. This would mean skipping the required id lookup, which means adding a new command:

az boards work-item relation add-url

Additional context

[roshan-sy]

Proposed solution
Instead of adding a new command, we can add a new parameter --target-url.
Cli will conditionally use between target-url and target-id

[roshan-sy]

Proposed solution Instead of adding a new command, we can add a new parameter --target-url. Cli will conditionally use between target-url and target-id

@asmundg Shall I go ahead with this approach?