Add just audit, just audit-fix, use these commands in CI (#582)

### What

The audit check is failing because of a problem in `sqlx` that is said
to be fixed in the next version. Until then, I guess this check just has
to be optional.

.github/workflows/cargo-audit.yaml

@@ -6,6 +6,8 @@ jobs:
   cargo_audit:
     name: cargo audit
     runs-on: ubuntu-latest
+    env:
+      CARGO_NET_GIT_FETCH_WITH_CLI: "true"
     steps:
       - uses: actions/checkout@v4
 
@@ -18,6 +20,17 @@ jobs:
               - "**/Cargo.lock"
 
       - if: steps.changes.outputs.cargo == 'true'
-        uses: actions-rs/audit-check@v1
+        name: Install `just`
+        uses: extractions/setup-just@v2
+
+      - if: steps.changes.outputs.cargo == 'true'
+        name: install tools
+        run: rustup show
+
+      - if: steps.changes.outputs.cargo == 'true'
+        uses: Swatinem/rust-cache@v2
         with:
-          token: ${{ secrets.GITHUB_TOKEN }}
+          shared-key: "build" # share the cache across jobs
+
+      - if: steps.changes.outputs.cargo == 'true'
+        run: just audit