Add new Client API

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

tests/plan/client/filesystem/conflict/test.cue

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"dagger.io/dagger"
+)
+
+dagger.#Plan & {
+	client: filesystem: "test.txt": {
+		// no dependencies between these two, one must be forced
+		read: contents:  string
+		write: contents: actions.test.export.contents
+	}
+	actions: {
+		image: dagger.#Pull & {
+			source: "alpine:3.15.0@sha256:e7d88de73db3d3fd9b2d63aa7f447a10fd0220b7cbf39803c803f2af9ba256b3"
+		}
+		test: {
+			read: dagger.#Exec & {
+				input: image.output
+				args: ["echo", client.filesystem."test.txt".read.contents]
+			}
+			write: dagger.#Exec & {
+				input: image.output
+				args: ["sh", "-c",
+					#"""
+						echo -n bar > /out.txt
+						"""#,
+				]
+			}
+			export: dagger.#ReadFile & {
+				input: write.output
+				path:  "out.txt"
+			}
+			// FIXME: hack until we can do outputs with `dagger do`
+			verify: dagger.#Exec & {
+				input: image.output
+				args: ["echo", client.filesystem."test.txt".write.contents]
+			}
+		}
+	}
+}