[BUG] Generator does not always implement necessary traits

[karencfv]

When updating the omicron version to e2bd1e8 to pull in changes made to the Global images API (which will be necessary to fix the images/global images commands), I hit this error:

error[E0277]: the trait bound `ImageSource: Default` is not satisfied
    --> oxide/src/types.rs:1344:5
     |
1307 | #[derive(Serialize, Deserialize, PartialEq, Debug, Clone, JsonSchema, Default, Tabled)]
     |                                                                       ------- in this derive macro expansion
...
1344 |     pub source: ImageSource,
     |     ^^^^^^^^^^^^^^^^^^^^^^^ the trait `Default` is not implemented for `ImageSource`
     |
     = note: this error originates in the derive macro `Default`

It seems the generator doesn't always implement necessary traits

[karencfv]

Fixed by oxidecomputer/oxide.rs#104