Introduce embedded BuildSpec for BuildRuns

Make `BuildRef` optional and generate CRDs and fix all occurrences.

Introduce code in `GetBuildObject` to support both the `BuildRef` approach and
the new `BuildSpec` option. Return a transient in-memory Build resource in case
the BuildRun has an embedded BuildSpec.

Add optional `BuildSpec` in BuildRun spec.

Add E2E test cases for embedded builds in buildruns.

Add new BuildRun validation option in docs.

Remove variable name for `context` to make it undefined (linter warning).

Add empty lines for readability.

Sort imports based on common kube/others order.

Replace copy/paste description with specific one for bundle tests.

Add `Expect`s to give human readable error in case test environment variables
are not set.

Remove duplicate import of `k8s.io/api/core/v1`.

Simplify code by removing the `if` check.

Fix warning that variable declaration could shadow previous variable value by
refactoring the respective `if` block.

Add or remove empty lines in `buildrun_test.go` to increase readability and to
keep the same style as in other test cases.

Refactor code to fix variable value shadow warning.

Replace generic `errors.New("not found")` with Kube specific one.

Introduce empty status call stub (not not fail in status update case).

Refactor return statement to be more simple.

Introduce `BuildSpec` in BuildRun spec

Refactor build reconciler logic by inlining `UpdateBuildStatusAndRetreat`
function that is only used once.

Add test case to cover special case for build resource not being in the system.

Refactor validation code by moving out validation list into a global variable.

Add convenience function to get the name of the referenced build.

Use `resources.GetBuildObject` instead of manual look-up in test cases.

Introduce controller-runtime Kubernetes client in test handle.

Add functions to create the validation structs in a consistent way.

Add convenience function to validate a Build with validation varargs.

Introduce validation code for field permutations.

Add test cases for field validation.

Fix markdown linter warnings and indention.

README.md

@@ -32,27 +32,27 @@ Shipwright supports any tool that can build container images in Kubernetes clust
 
 ## Try It!
 
-* We assume you already have a Kubernetes cluster (v1.20+). If you don't, you can use [KinD](https://kind.sigs.k8s.io), which you can install by running [`./hack/install-kind.sh`](./hack/install-kind.sh).
+- We assume you already have a Kubernetes cluster (v1.20+). If you don't, you can use [KinD](https://kind.sigs.k8s.io), which you can install by running [`./hack/install-kind.sh`](./hack/install-kind.sh).
 
-* We also require a Tekton installation (v0.27+). To install the newest supported version, run:
+- We also require a Tekton installation (v0.27+). To install the newest supported version, run:
 
  ```bash
  kubectl apply --filename https://storage.googleapis.com/tekton-releases/pipeline/previous/v0.30.0/release.yaml
  ```
 
-* Install the Shipwright deployment. To install the latest version, run:
+- Install the Shipwright deployment. To install the latest version, run:
 
  ```bash
  kubectl apply --filename https:/shipwright-io/build/releases/download/v0.8.0/release.yaml
  ```
 
-* Install the Shipwright strategies. To install the latest version, run:
+- Install the Shipwright strategies. To install the latest version, run:
 
  ```bash
  kubectl apply --filename https:/shipwright-io/build/releases/download/v0.8.0/sample-strategies.yaml
  ```
 
-* Generate a secret to access your container registry, such as one on [Docker Hub](https://hub.docker.com/) or [Quay.io](https://quay.io/):
+- Generate a secret to access your container registry, such as one on [Docker Hub](https://hub.docker.com/) or [Quay.io](https://quay.io/):
 
  ```bash
  REGISTRY_SERVER=https://index.docker.io/v1/ REGISTRY_USER=<your_registry_user> REGISTRY_PASSWORD=<your_registry_password>
@@ -63,7 +63,7 @@ Shipwright supports any tool that can build container images in Kubernetes clust
  --docker-email=<your_email>
  ```
 
-* Create a *Build* object, replacing `<REGISTRY_ORG>` with the registry username your `push-secret` secret have access to:
+- Create a *Build* object, replacing `<REGISTRY_ORG>` with the registry username your `push-secret` secret have access to:
 
  ```bash
  REGISTRY_ORG=<your_registry_org>
@@ -86,15 +86,16 @@ Shipwright supports any tool that can build container images in Kubernetes clust
  EOF
  ```
 
-To view the *Build* which you just created:
+ To view the *Build* which you just created:
 
- ```
- $ kubectl get builds
+ ```bash
+  $ kubectl get builds
  
  NAME REGISTERED REASON BUILDSTRATEGYKIND BUILDSTRATEGYNAME CREATIONTIME
  buildpack-nodejs-build True Succeeded ClusterBuildStrategy buildpacks-v3 68s
  ``` 
-* Submit your *BuildRun*:
+
+- Submit your *BuildRun*:
 
  ```bash
  cat <<EOF | kubectl create -f -
@@ -108,9 +109,9 @@ To view the *Build* which you just created:
  EOF
  ```
 
-* Wait until your *BuildRun* is completed and then you can view it as follows:
+- Wait until your *BuildRun* is completed and then you can view it as follows:
 
- ```
+ ```bash
  $ kubectl get buildruns
  
  NAME SUCCEEDED REASON STARTTIME COMPLETIONTIME
@@ -123,7 +124,7 @@ To view the *Build* which you just created:
  kubectl get buildrun --output name | xargs kubectl wait --for=condition=Succeeded --timeout=180s
  ```
 
-* After your *BuildRun* is completed, check your container registry, you will find the new generated image uploaded there.
+- After your *BuildRun* is completed, check your container registry, you will find the new generated image uploaded there.
 
 ## Please tell us more!
 
@@ -175,16 +176,16 @@ Our sample build strategies are all functional on linux/amd64. Their support on
 
 We host weekly meetings for users, contributors, maintainers and anyone interested in the project. The weekly meetings take place on Mondays at 1pm UTC.
 
-* Meeting [minutes](https:/shipwright-io/community/issues?q=is%3Aissue+label%3Acommunity+label%3Ameeting)
-* Public calendar [invite](https://calendar.google.com/calendar/u/1?cid=Y19iMWVndjc3anUyczJkbWNkM2R1ZnAxazhuNEBncm91cC5jYWxlbmRhci5nb29nbGUuY29t)
+- Meeting [minutes](https:/shipwright-io/community/issues?q=is%3Aissue+label%3Acommunity+label%3Ameeting)
+- Public calendar [invite](https://calendar.google.com/calendar/u/1?cid=Y19iMWVndjc3anUyczJkbWNkM2R1ZnAxazhuNEBncm91cC5jYWxlbmRhci5nb29nbGUuY29t)
 
 ### Want to contribute
 
 We are so excited to have you!
 
-* See [CONTRIBUTING.md](CONTRIBUTING.md) for an overview of our processes
-* See [DEVELOPMENT.md](DEVELOPMENT.md) for how to get started
-* See [HACK.md](HACK.md) for how to build, test & run
+- See [CONTRIBUTING.md](CONTRIBUTING.md) for an overview of our processes
+- See [DEVELOPMENT.md](DEVELOPMENT.md) for how to get started
+- See [HACK.md](HACK.md) for how to build, test & run
  (advanced reading material)
 - Look at our
  [good first issues](https:/shipwright-io/build/issues?q=is%3Aissue+is%3Aopen+label%3A%22good+first+issue%22)