fix(docs): filter Optional markers from validation column

The crd-ref-docs tool v0.3.0 introduced a change that started
rendering `+optional` Go code markers as `Optional: {}` in the
validation column of API documentation. This appeared as an empty JSON
object and was redundant since the Required column already displayed
this information. This updates the documentation template to filter
out these Optional markers while preserving meaningful validation
rules like patterns and enums. It also removes redundant customMarkers
configuration.

Closes #722

Signed-off-by: Marco Nenciarini <marco.nenciarini@enterprisedb.com>

Taskfile.yml

@@ -86,7 +86,7 @@ tasks:
       # renovate: datasource=git-refs depName=crd-gen-refs lookupName=https://github.com/cloudnative-pg/daggerverse currentValue=main
       DAGGER_CRDGENREF_SHA: ee59e34a99940e45f87a16177b1d640975b05b74
       # renovate: datasource=go depName=github.com/elastic/crd-ref-docs
-      CRDREFDOCS_VERSION: v0.2.0
+      CRDREFDOCS_VERSION: v0.3.0
     cmds:
       - >
         GITHUB_REF= dagger -s call -m github.com/cloudnative-pg/daggerverse/crd-ref-docs@${DAGGER_CRDGENREF_SHA}

hack/crd-gen-refs/config.yaml

@@ -1,9 +1,6 @@
 processor:
   ignoreGroupVersions:
     - "GVK"
-  customMarkers:
-    - name: "optional"
-      target: field
   ignoreFields:
 #    - "status$"
     - "TypeMeta$"

hack/crd-gen-refs/markdown/type.tpl

@@ -31,7 +31,7 @@ _Appears in:_
 {{ end -}}
 
 {{ range $type.Members -}}
-| `{{ .Name  }}` _{{ markdownRenderType .Type }}_ | {{ template "type_members" . }} | {{ if not .Markers.optional -}}True{{- end }} | {{ markdownRenderDefault .Default }} | {{ range .Validation -}} {{ markdownRenderFieldDoc . }} <br />{{ end }} |
+| `{{ .Name  }}` _{{ markdownRenderType .Type }}_ | {{ template "type_members" . }} | {{ if not .Markers.optional -}}True{{- end }} | {{ markdownRenderDefault .Default }} | {{ range .Validation -}}{{- $v := markdownRenderFieldDoc . }}{{- if and $v (ne $v "Optional: {}") (ne $v "Optional: \\{\\}") -}} {{ $v }} <br />{{ end }}{{- end }} |
 {{ end -}}
 
 {{ end -}}