Google AI Gemini Spring Boot Starter

[emredmrcan]

Issue

Closes langchain4j/langchain4j#2103

Change

A new Spring Boot starter module named langchain4j-google-ai-gemini-spring-boot-starter was added.
This includes creating auto-configuration classes and properties to facilitate easy setup and management of Google AI Gemini within the LangChain4j.
The root pom.xml was updated to include the new module.
An import file for auto-configuration was created to facilitate Spring Boot's configuration process.

General checklist

• There are no breaking changes
• I have added unit and/or integration tests for my change
• The tests cover both positive and negative cases
• I have manually run all the unit and integration tests in the module I have added/changed, and they are all green

• I have added/updated the documentation
• I have added an example in the examples repo (only for "big" features)

Checklist for adding new Spring Boot starter

• I have added my new starter in the root pom.xml
• I have added a org.springframework.boot.autoconfigure.AutoConfiguration.imports file in the langchain4j-{integration}-spring-boot-starter/src/main/resources/META-INF/spring/ directory

[ddobrin]

Hi @emredmrcan,
for your reference, there is PR #74 opened for the same langchain4j/langchain4j#2103