does someone have an example of (any) resource being created with user-assigned identity?

There's an issue thread about user identity at https://github.com/pulumi/pulumi-azure-native/issues/812. Maybe something in there might help, looks like a lot of suggestions.

thanks. that does seem to have some help, though I've picked a particularly annoying example, since the Language service is

InputMap<UserAssignedIdentityArgs>

instead of

InputMap<object>

which means you can't assign the wonderful

Dictionary<string, object>

that serializes to

{}