cli: reject `rad id` proposals that do not verify — heartwood

To ensure that the rad id command does not modify the project payload without it being able to be deserialized into the Project type, the command performs this check throught the project method, and returns an error if this fails.

    "threshold": 1
  }
 ```
 Note that we cannot delete mandatory fields:
 ``` (fails)
 $ rad id update --title "Delete default branch" --payload xyz.radicle.project defaultBranch null
 ✗ Error: failed to verify `xyz.radicle.project`, failed with json: missing field `defaultBranch`
 ```

                         anyhow::bail!("payload `{id}` not found in identity document");
                     }
                 }
                 // Verify that the project payload can still be parsed into the
                 // `Project` type.
                 if let Err(e) = proposal.project() {
                     anyhow::bail!("failed to verify `xyz.radicle.project`, failed with {e}",);
                 }
                 proposal
             };
             if proposal == current.doc {