doc: CRD scope requires fixes and improvements

[camilamacedo86]

Bug Report

• we need to improve the doc to make it more clear. See: https://master.sdk.operatorframework.io/docs/building-operators/golang/crds-scope/
• we can link k8s reference to describe what CRD cluster and namespaced scope means
• the marker there is wrong. It is: // +kubebuilder:resource:scope=Cluster. Example

// +kubebuilder:object:root=true
// +kubebuilder:subresource:status
// +kubebuilder:resource:scope=Cluster

// Memcached2 is the Schema for the memcached2s API
type Memcached2 struct {
	metav1.TypeMeta   `json:",inline"`
	metav1.ObjectMeta `json:"metadata,omitempty"`

	Spec   Memcached2Spec   `json:"spec,omitempty"`
	Status Memcached2Status `json:"status,omitempty"`
}

• Also, we ought to tell to the users that to generated Cluster scoped CRD's the can use the flag --namespaced=false E.g

$ operator-sdk create api --group cache --version v1 --kind Memcached2 --resource=true --controller=true --namespaced=false

• And then, that by default they are namespaced scope which means that no requires marker at all.

[openshift-bot]

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[camilamacedo86]

/lifecycle frozen

[estroz]

Two things need to be done here:

1. Link the CRD scoped.
2. Documented --namespaced.

[estroz]

Closed by #4812