Supporting multiple LLMs in auto-config

[ddobrin]

Currently, proprietary or open models running in Google Vertex can be accessed through the Vertex Gemini module, respectively using the OpenAI API.

#################################
# Google Vertex AI Gemini
#################################
spring.ai.vertex.ai.gemini.project-id=<project>
spring.ai.vertex.ai.gemini.location=us-central1
spring.ai.vertex.ai.gemini.chat.options.model=gemini-2.0-flash-001
spring.ai.vertex.ai.gemini.transport=grpc

#################################
# OpenAI API VertexAI
#################################
spring.ai.openai.api-key=abc123
spring.ai.openai.vertex.ai.gemini.project-id=<project>
spring.ai.openai.vertex.ai.gemini.location=us-central1
spring.ai.openai.vertex.ai.chat.options.model=meta/llama3-405b-instruct-maas
spring.ai.openai.vertex.ai.chat.base-url=<baseURL>
spring.ai.openai.vertex.ai.chat.completions-path=/chat/completions
spring.ai.openai.vertex.ai.chat.options.max-tokens=1024

The problem - there is no ability to auto-config more than 1 Gemini or open model in Vertex at this time.

The proposal - introduce the ability to add a in the auto-config, to allow for multiple configurations

spring.ai.vertex.ai.gemini.<gemini-flash>.project-id=<project>
spring.ai.vertex.ai.gemini.<gemini-flash>.location=us-central1
spring.ai.vertex.ai.gemini.<gemini-flash>.chat.options.model=gemini-2.0-flash-001
spring.ai.vertex.ai.gemini.<gemini-flash>.transport=grpc

spring.ai.vertex.ai.gemini.<gemini-pro>.project-id=<project>
spring.ai.vertex.ai.gemini.<gemini-pro>.location=us-central1
spring.ai.vertex.ai.gemini.<gemini-pro>.chat.options.model=gemini-1.5-001
spring.ai.vertex.ai.gemini.<gemini-pro>.transport=grpc

Workaround - not using auto-config and manually configuring each model in use

CC @tzolov

[ThomasVitale]

I would really like to have this possibility in Spring AI. Unfortunately, I'm afraid it's up to the Spring Boot project to support registering multiple beans of the same type via auto-configuration, a capability that so far has not been supported by Spring Boot.

I hope things will change in Spring Boot 4, based on the new changes introduced in Spring Framework 7 for programmatically registering beans, that would enable such functionality (https://docs.spring.io/spring-framework/reference/7.0/core/beans/java/programmatic-bean-registration.html). See spring-projects/spring-boot#15732.