Consistently allow for aiModelWebClientBuilder

[poutsma]

This PR ensures that all subclasses of OpenAiCompatibleModelFactory have a webClientBuilder: ObjectProvider<WebClient.Builder> constructor parameter, so that users can configure WebClient (e.g. for OAuth2 or custom authentication) without having to bypass autoconfiguration.

Closes gh-1584

[poutsma]

@alexheifetz I wasn't sure if the aiModelWebClientBuilder bean definition in NettyClientAutoConfiguration is a good idea or not, please advise. It does pull in a webflux dependency.

[alexheifetz]

i think having compile dependency on spring-webflux should be OK

Here is why:

1. Model Providers (via spring-ai) already bring in spring-webflux dependencies into the Maven Reactor
2. Netty Autocofiguration is an optional addition on top of Model Providers, therefore new dependency on spring-webflux does not really change runtime composition of the application.

[simeshev]

@poutsma, do we care about Javadocs for public methods?

[poutsma]

@poutsma, do we care about Javadocs for public methods?

It depends :). I do care about documentation for public, user-facing API methods, but the changes made in this PR do not fall in that category. The only new public method this PR introduces is a @Bean declaration, which is not meant for user consumption. Moreover, the existing aiModelHttpRequestFactory bean declaration in NettyClientAutoConfiguration did not have documentation either, so for consistency I would have to introduce it for that method as well, thus obscuring the goal of this PR.