Include a serde feature in the shared crate

.drone.yml

@@ -4,26 +4,21 @@ name: default
 
 steps:
   - name: build
-    image: rust:1.68
+    image: rust:1.77
     commands:
       - cargo build
-    volumes:
+    volumes: &caches
       - name: cargo-cache
         path: /cache/cargo
-    environment:
+    environment: &env
       CARGO_HOME: /cache/cargo
-      CARGO_REGISTRIES_CRATES_IO_PROTOCOL: sparse
 
   - name: test
-    image: rust:1.68
+    image: rust:1.77
     commands:
       - cargo test --all-features
-    volumes:
-      - name: cargo-cache
-        path: /cache/cargo
-    environment:
-      CARGO_HOME: /cache/cargo
-      CARGO_REGISTRIES_CRATES_IO_PROTOCOL: sparse
+    volumes: *caches
+    environment: *env
     depends_on:
       - build