Fix deserialization with some attributes

The "repository" field doesn't have a type right now, so I'm going to
skip deserializing it. The returned JSON has a value for this field, but
Serde will ignore it.

The `Packages.pkg_type` field is called "type" in the JSON string (and
Go code, as mentioned in the comment). Similarly, the PackageType enum
I have to represent this field in Rust has capital starting letters
where the JSON uses all lowercase. Both problems are solved with a Serde
rename attribute.

src/structs/package.rs

@@ -14,8 +14,10 @@ pub struct Package {
     id: u64,
     name: String,
     owner: Author,
+    #[serde(skip)]
     repository: (),             // TODO: Create a `struct Repository`
-    pkg_type: PackageType,      // field is "type" in Go, but that's a keyword in Rust.
+    #[serde(rename = "type")]   // field is "type" in JSON & Go, but that's a
+    pkg_type: PackageType,      // keyword in Rust so we need to serde-rename it.
     version: String,
 }
 
@@ -37,6 +39,7 @@ impl Package {
 
 /// A marker for the kind of package being handled.
 #[derive(Debug, Deserialize, Serialize)]
+#[serde(rename_all = "snake_case")]
 pub enum PackageType {
     Alpine,
     Arch,