chore: FromStr impl to convert str to StorageClass enum (#13)

src/types.rs

@@ -1,4 +1,4 @@
-use std::time::Duration;
+use std::{str::FromStr, time::Duration};
 
 use typed_builder::TypedBuilder;
 
@@ -128,6 +128,18 @@ impl From<api::StorageClass> for StorageClass {
     }
 }
 
+impl FromStr for StorageClass {
+    type Err = ConvertError;
+    fn from_str(value: &str) -> Result<Self, Self::Err> {
+        match value {
+            "unspecified" => Ok(Self::Unspecified),
+            "standard" => Ok(Self::Standard),
+            "express" => Ok(Self::Express),
+            _ => Err("invalid storage class value".into()),
+        }
+    }
+}
+
 impl From<StorageClass> for i32 {
     fn from(value: StorageClass) -> Self {
         api::StorageClass::from(value).into()