Use methods from HttpHeaders which are available both from Spring 6 and Spring 7

[filiphr]

I know that Spring AI 1.x is only compatible with Spring Boot 3 and Spring 6. However, we are trying to migrate to Spring Boot 4 and keep using Spring AI 1.x. Once Spring AI 2.x is released we are going to migrate to it.

However, in the meantime it is not possible due to few things:

• Spring Boot 4 - big restructure of it's modules. This is OK, since we could create our own auto configurations for what we need
• Spring Web HttpHeaders - Use of certain methods from HttpHeaders which are no longer available in Spring 7.

This PR is trying to use alternative methods which are available both in Spring 6 and Spring 7. This means that things like the OpenAiAPI, AnthropicApi etc. can still be used on Spring 7.

I hope that you can consider this PR and consider porting it to Spring AI 1.1.

[ericbottard]

Hi @filiphr,

thanks for your PR that could be a good first step indeed.

Forcing the use of spring-web 7 though (by adding

			<dependency>
				<groupId>org.springframework</groupId>
				<artifactId>spring-web</artifactId>
				<version>7.0.0-M8</version>
			</dependency>

in the dependencies sections), and after skipping over some other deprecations, I still get a couple of wrong API usages (in hugging-face first, but there could be others).

Could you take a look and try to cover the last extra mile?

[filiphr]

Thanks for reviewing @ericbottard, there were indeed some more spring-web 7 compilation problems. I have that fixed locally. I'll push it. I can also push a GitHub workflow that will run a compile with Spring 7.

[filiphr]

@ericbottard I've done the additional adjustments so that the entire code base can compile with Spring 7. I also added a GitHub workflow build so that a PR check is run with the compilation.

The "biggest" change is the ApiClient.mustache. I put it in quotes, since that file is the most amount of lines, but if you actually compare it with the one from the Swagger Codegen you'll see that the change is one or 2 lines around the header checks.

Let me know what you think