Allow the `sub` for a user-jwt to be set, independent of the `name`

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

I want to create a user-jwt with a specific `sub`, but when I do the following:

```sh
dotnet user-jwts create --claim "sub=1" --valid-for 3650d
```

The `sub` ends up as:

```json
"sub": [
"Glen",
"1"
]
```

The name should not be included in the `sub` if there is already a value.

### Describe the solution you'd like

Avoid inserting a value for `sub` if one has already been set.

### Additional context

_No response_