docs: update developer guide

docs/developer-guide.md

 # Developer Guide
 
 ## Prerequisites
-- a well prepared kubernetes cluster. Follow the [instructions](https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/) to create a kubernetes cluster, or create a local kubernetes node referring to [kind](https://kind.sigs.k8s.io/docs/user/quick-start/) or [minikube](https://minikube.sigs.k8s.io/docs/start/)
+
+- a well prepared kubernetes cluster. Follow the[instructions](https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/) to create a kubernetes cluster, or create a local kubernetes node referring to[kind](https://kind.sigs.k8s.io/docs/user/quick-start/) or[minikube](https://minikube.sigs.k8s.io/docs/start/)
 - kustomize. Installed by the following command
+
 ```bash
 curl -s "https://raw.githubusercontent.com/\
 kubernetes-sigs/kustomize/master/hack/install_kustomize.sh"  | bash
 ```
-- cert-manager. Installation on kubernetes referenced to [cert-manager docs](https://cert-manager.io/docs/installation/kubernetes/). Or you can install by the following command.
-```bash
-kubectl create -f ./config/certmanager/cert-manager.yaml
-```
-## Project Initialization
-This project is based on [kubebuilder v3](https://github.com/kubernetes-sigs/kubebuilder/releases/download/v3.0.0/kubebuilder_linux_amd64), since CRDs generated by kubebuilder v2 is not compatible in kubernetes v1.20.
-```bash
-kubebuilder init --domain opendilab.org --license apache2 --owner "The OpenDILab authors"
 
-kubebuilder create api --group diengine --version v1alpha2 --kind DIJob
+## CRD Design
 
-kubebuilder create api --group diengine --version v1alpha2 --kind AggregatorConfig
-```
+Update codes in [dijob_types.go](./api/v1alpha2/dijob_types.go) with your requirements, and generate deepcopy functions.
 
-## CRD Design
-Make codes in [dijob_types.go](./api/v1alpha2/dijob_types.go) and [aggregatorconfig_types.go](./api/v1alpha2/aggregatorconfig.go) with your requirements, and generate deepcopy functions.
 ```bash
 make generate
 ```
+
 Generate new CRD files with the following command.
+
 ```bash
 make manifests
 ```
+
 New CRD files will be generated in [./config/crd/bases](./config/crd/bases)
 
 ## Controller Logic
+
 Referenced to [controllers](./controllers)
 
 ## DI Server Logic
+
 Referenced to [server](./server)
 
 ## Installation
 
 Run the following command in the project root directory.
+
 ```bash
 # build images. 
 make docker-build
@@ -48,26 +45,31 @@ make docker-push
 # deploy di-operator and server to cluster
 make dev-deploy
 ```
+
 Since the CustomResourceDefinitions are too long, you will probably find the following error:
+
 ```bash
 The CustomResourceDefinition "dijobs.diengine.opendilab.org" is invalid: metadata.annotations: Too long: must have at most 262144 bytes
 ```
 
 Then running the following command will solve the problem:
+
 ```bash
 kustomize build config/crd | kubectl create -f -
 ```
 
-`di-operator`, `di-webhook` and `di-server` will be installed in `di-system` namespace. 
+`di-operator` and `di-server` will be installed in `di-system` namespace.
+
 ```bash
 $ kubectl get pod -n di-system
 NAME                               READY   STATUS    RESTARTS   AGE
 di-operator-57cc65d5c9-5vnvn       1/1     Running   0          59s
 di-server-7b86ff8df4-jfgmp         1/1     Running   0          59s
-di-webhook-45jgi23fhc-9yght        1/1     Running   0          59s
 ```
 
-Install global components of DIJob defined in AggregatorConfig:
-```bash
-kubectl create -f config/samples/agconfig.yaml -n di-system
-```
+## Programming Specification
+
+- Logger: logger should use`github.com/go-logr/logr.Logger`, created from`sigs.k8s.io/controller-runtime/pkg/log.DelegatingLogger`. We have the following specifications
+  - Logger used in each function should be defined as:`logger := ctx.Log.WithName(function-name).WithValues("job", job-namespace-name))`. It's helpful for debuging since we can easily locate where the log message is from and what the DIJob is. Then, DIJob related information is not needed in log message.
+  - All the log message should start with lower case letter.
+  -