Add new Client API

Signed-off-by: Helder Correia <174525+helderco@users.noreply.github.com>

tests/plan/client/filesystem/read/service/valid.cue

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"dagger.io/dagger"
+)
+
+dagger.#Plan & {
+	client: filesystem: "/var/run/docker.sock": read: contents: dagger.#Service
+
+	actions: {
+		image: dagger.#Pull & {
+			source: "alpine:3.15.0@sha256:e7d88de73db3d3fd9b2d63aa7f447a10fd0220b7cbf39803c803f2af9ba256b3"
+		}
+
+		imageWithDocker: dagger.#Exec & {
+			input: image.output
+			args: ["apk", "add", "--no-cache", "docker-cli"]
+		}
+
+		test: dagger.#Exec & {
+			input: imageWithDocker.output
+			mounts: docker: {
+				dest:     "/var/run/docker.sock"
+				contents: client.filesystem."/var/run/docker.sock".read.contents
+			}
+			args: ["docker", "info"]
+		}
+	}
+}