kbs: add default value for config deserialization

Before this commit, if we do not explicitly specify the `dir_path` when
using localfs resource storage, the launch of kbs will fail. This commit
adds a default value when kbs tries to read config. If no value is given
it will use the default value.

Signed-off-by: Xynnn007 <[email protected]>

kbs/src/plugins/implementations/resource/local_fs.rs

@@ -14,6 +14,7 @@ pub const DEFAULT_REPO_DIR_PATH: &str = "/opt/confidential-containers/kbs/reposi
 
 #[derive(Debug, Deserialize, Clone, PartialEq)]
 pub struct LocalFsRepoDesc {
+    #[serde(default)]
     pub dir_path: String,
 }