engine.#Build: support auth

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

tests/tasks.bats

@@ -85,4 +85,6 @@ setup() {
     "$DAGGER" --europa up ./image_config.cue
     "$DAGGER" --europa up ./labels.cue
     "$DAGGER" --europa up ./platform.cue
+
+    "$DAGGER" --europa up ./build_auth.cue
 }

tests/tasks/build/build_auth.cue

@@ -0,0 +1,24 @@
+package testing
+
+import (
+	"alpha.dagger.io/europa/dagger/engine"
+)
+
+engine.#Plan & {
+	inputs: {
+		directories: testdata: path:     "./testdata"
+		secrets: dockerHubToken: envvar: "DOCKERHUB_TOKEN"
+	}
+
+	actions: build: engine.#Build & {
+		source: inputs.directories.testdata.contents
+		auth: [{
+			target:   "daggerio/ci-test:private-pull"
+			username: "daggertest"
+			secret:   inputs.secrets.dockerHubToken.contents
+		}]
+		dockerfile: contents: """
+			FROM daggerio/ci-test:private-pull@sha256:c74f1b1166784193ea6c8f9440263b9be6cae07dfe35e32a5df7a31358ac2060
+			"""
+	}
+}