Is your feature request related to a problem? Please describe.

Hello springdoc team, I would like to suggest the feature on SpecPropertiesCustomizer.

• I'm using the SpecPropertiesCustomizer when configuring groupedOpenApi. I tried the external-docs property on the group-configs but it seems like doesn't configure actually.

springdoc:
  group-configs:
    - group: api1
      open-api:
        info:
          title: "API 1"
        external-docs:
          url: https://docs.github.com/en/rest/branches/branches?apiVersion=2022-11-28
          description: "Github API Documentation"
    - group: api2
      open-api:
        info:
          title: "API 2"

Describe the solution you'd like

• I want to configure the external-docs property that I described on the group-config

Describe alternatives you've considered

• I just think that implement the configureExternalDocs function on the SpecPropertiesCustomizer class can support this feature.

Additional context

• I want to know that it is no problem to add this feature without side effect.
• If it is possible to support this feature may I contribute to springdoc-openapi?

Thanks 🙇