Changes rock base to bare

Switching to a bare-based image will reduce the overall image size
and reduces attack surface area.

Adding the ``CGO_ENABLED=0`` will result in the go binary being
statically linked, which means it won't need the ``/lib`` and ``/lib64``
folders to run. This allows us to switch the base image to bare, greatly
reducing the image size.

Adds an extra sanity check during the integration test, making sure that
there is no error reported in Pebble while starting the service.

rockcraft.yaml

@@ -18,7 +18,7 @@ description: |
 license: Apache-2.0
 version: 0.0.1
 
-base: [email protected]
+base: bare
 build-base: [email protected]
 run-user: _daemon_
 
@@ -48,6 +48,7 @@ parts:
     build-environment:
       - GOOS: linux
       - GOARCH: $CRAFT_ARCH_BUILD_FOR
+      - CGO_ENABLED: 0
     go-generate:
       - ./cmd
     organize:

tests/integration/test_mutating_pebble_webhook.py

@@ -82,6 +82,23 @@ def webhook_instance(module_instance: harness.Instance):
         module_instance, "mutating-pebble-webhook", "pebble-webhook"
     )
 
+    # Sanity check: make sure there isn't an error in Pebble that it couldn't start the service.
+    process = module_instance.exec(
+        [
+            "k8s",
+            "kubectl",
+            "logs",
+            "-n",
+            "pebble-webhook",
+            "deployment.apps/mutating-pebble-webhook",
+        ],
+        check=True,
+        capture_output=True,
+        text=True,
+    )
+
+    assert '(Start service "mutating-pebble-webhook") failed' not in process.stdout
+
     yield module_instance