feat: Orchestration Prompt

[MatKuhr]

Context

AI/ai-sdk-java-backlog#55.

This PR introduces OrchestrationPrompt to allow for more convenient orchestration usage.

Soft prerequisite: #141

API Improvement

Before:

LLMModuleConfig llmConfig;
ChatMessage userMessage;

var template = TemplatingModuleConfig.create().template(userMessage);
var config = ModuleConfigs.create().llmModuleConfig(llmConfig).templatingModuleConfig(template);

var request =
    CompletionPostRequest.create()
        .orchestrationConfig(OrchestrationConfig.create().moduleConfigurations(config));

new OrchestrationClient().chatCompletion(request);

After:

LLMModuleConfig llmConfig;
ChatMessage userMessage;

var prompt = new OrchestrationPrompt(userMessage);
var config = new OrchestrationModuleConfig().withLlmConfig(llmConfig);

new OrchestrationClient().chatCompletion(prompt, config);

Feature scope:

• OrchestrationPrompt with convenience overloads for string and varargs
• Reusable OrchestrationModuleConfig object

Definition of Done

• Functionality scope stated & covered
• Tests cover the scope above
• Error handling created / updated & covered by the tests above
• Aligned changes with the JavaScript SDK
• Documentation updated
• Release notes updated

[MatKuhr]

temporary, will be increased again after tests have been refactored in a separate PR