Add configuration file format selection (properties/yaml)

[MeRitik]

Adds a wizard step allowing users to choose the Spring Boot configuration file format (application.properties or application.yaml).

Details

Spring Initializr supports selecting configuration file format via the configurationFileFormat parameter. This change:

• Introduces a new wizard step after packaging selection
• Allows choosing between Properties and YAML formats
• Defaults to Properties to preserve existing behaviour
• Adds configurable default via spring.initializr.defaultConfigurationFileFormat

Fixes #267

[MeRitik]

@microsoft-github-policy-service agree

[MeRitik]

Here's the demo

[NeryCif-20]

Hi! Just checking in on this PR. This feature would be super helpful for those of us who prefer using YAML files from the start. Is there any update on this, or is there anything needed to help get it reviewed and merged? Thanks for your work on this extension!

[MeRitik]

Hi! Just checking in on this PR. This feature would be super helpful for those of us who prefer using YAML files from the start. Is there any update on this, or is there anything needed to help get it reviewed and merged? Thanks for your work on this extension!

Thanks for checking in! Just rebased and resolved conflicts with main, and tested the change. It works as expected (wizard step shows Properties/YAML choice, respects the defaultConfigurationFileFormat setting, and generates the correct file). Ready for review whenever a maintainer has a chance to take a look — happy to make any changes requested.