Allow OpenAPI customizers to run even for cached OpenAPI documents

[emilchitas]

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

We have a service which is accessible through a wildcard domain (*.example.com), and users can access this system with some specific prefixes (e.g. prefixA.example.com, prefixB.example.com).
When serving the OpenAPI document, we make use of the OpenAPICustomizer(s) to customize the server URL to also include the common path of the APIs present in that document.

This was possible, until the logic to be able to customize also cached OpenAPI documents was reverted with this PR.
Now, even if a client would access the document with the https://prefixB.example.com, it would be served the cached OpenAPI with the https://prefixA.example.com/my/foo server URL, which was generated when it was first accessed.

Describe the solution you'd like

• We would like to have the possibility to register some customizer which would run also for cached OpenAPI's.

Describe alternatives you've considered

• This can be worked around by disabling the cache, but generating the whole OpenAPI on each request gets pretty expensive, the more this grows.

[bnasslahsen]

@emilchitas,

You can use ServerBaseUrlCustomizer.
Cache is not applied to it.

This is a sample code:

	@Bean
	ServerBaseUrlCustomizer serverBaseUrlCustomizer(){
		return serverBaseUrl -> serverBaseUrl.replace(serverBaseUrl,  UUID.randomUUID().toString());
	}

[emilchitas]

Thanks.
This fits well for our use case.