http: Make the rust github workflow throw errors instead of warnings

Instead of failing silently, warnings should be treated as errors and be
fixed before merging a patch.

.github/workflows/check-radicle-httpd.yml

@@ -16,6 +16,8 @@ jobs:
           workspaces: radicle-httpd -> target
       - name: Build
         run: cargo build --all-features
+        env:
+          RUSTFLAGS: -D warnings
       - name: Run tests
         run: cargo test --all-features
   docs:
@@ -31,7 +33,9 @@ jobs:
         with:
           workspaces: radicle-httpd -> target
       - name: Docs
-        run: cargo doc --all --all-features
+        run: cargo doc --all-features
+        env:
+          RUSTDOCFLAGS: -D warnings
   lint:
     name: Lint
     runs-on: ubuntu-latest
@@ -45,6 +49,8 @@ jobs:
         with:
           workspaces: radicle-httpd -> target
       - name: Run clippy
-        run: cargo clippy --all --tests
+        run: cargo clippy --tests
+        env:
+          RUSTFLAGS: -D warnings
       - name: Check formatting
-        run: cargo fmt --all --check
+        run: cargo fmt -- --check