Feat(workflow): Add op.#Task action (#2220)

* Feat(workflow): tekton task

* Feat(tools): random string

* Fix(example): defintion fmt

* Fix(rand): gosec weak random

docs/examples/workflow/source-to-image/step-definition.yaml

@@ -0,0 +1,55 @@
+apiVersion: core.oam.dev/v1beta1
+kind: WorkflowStepDefinition
+metadata:
+  name: build
+  namespace: vela-system
+spec:
+  schematic:
+    cue:
+      template: |-
+        import ("vela/op")
+
+        parameter: {
+           repoUrl: string
+           dockerfile: string
+           image: string
+        }
+
+        let pushImage=image
+
+        build: op.#Task & {
+                name:      "\(context.name)-\(context.stepId)"
+                namespace: context.namespace
+
+                // Declare workspaces that used to share data.
+                workspace: {
+                        "code-dir": {}
+                }
+
+                steps: [
+                        // git clone code repo.
+                        {
+                                name:  "git-clone"
+                                image: "git-image-with-pull-ssh"
+                                workspaceMounts: [{workspace: workspace["code-dir"], mountPath: "/data/code"}]
+                                script: """
+                #! /bin/bash
+                git clone \(repourl) /data/code
+                """
+                        },
+                        // build and push image.
+                        {
+                                name:  "build-image"
+                                image: "gcr.io/kaniko-project/executor:v1.3.0"
+                                workspaceMounts: [{workspace: workspace["code-dir"], mountPath: "/data/build"}]
+                                script: """
+                #! /bin/bash
+                /kaniko/executor --dockerfile=/data/build/\(dockerfile) --context=/data/build --destination=\(pushImage)
+                """
+                        }]
+        }
+
+        // wait until deployment ready
+        wait: op.#ConditionalWait & {
+           continue: build.do.status.phase == "successed"
+        }