ci: enable testnet integration suite

We don't want to hammer on public endpoints on every test run
indefinitely, but given that we're in the midst of a significant
refactor, having the new HTTPS-enabled integration tests running in CI
will save developer attention by running them automatically.

Author: conorsch

.github/workflows/rust.yml

@@ -79,3 +79,32 @@ jobs:
       # Build each crate separately, to validate that the feature-gating is working.
       # This is a lighter-weight version of `cargo check-all-features --workspace --release`.
       - run: ./deployments/scripts/check-crate-feature-sets
+
+  # Integration tests that run against the public testnet endpoints.
+  # Temporarily enabling these in CI, to provide assurance during refactoring.
+  testnet-integration:
+    runs-on: buildjet-16vcpu-ubuntu-2204
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          lfs: true
+
+      - name: install nix
+        uses: nixbuild/nix-quick-install-action@v28
+
+      - name: setup nix cache
+        uses: nix-community/cache-nix-action@v5
+        with:
+          primary-key: nix-${{ runner.os }}-${{ hashFiles('**/*.nix') }}
+          restore-prefixes-first-match: nix-${{ runner.os }}-
+          backend: buildjet
+
+      - name: Load rust cache
+        uses: astriaorg/buildjet-rust-cache@v2.5.1
+
+      # Confirm that the nix devshell is buildable and runs at all.
+      - name: validate nix env
+        run: nix develop --command echo hello
+
+      - name: run the testnet integration tests
+        run: nix develop --command just integration-testnet