feat: Add OpenAPI spec validation action and configure Spring profiles

[egekocabas]

Motivation

Prevent manual changes to autogenerated client code and ensure REST endpoint updates are reflected in the OpenAPI YAML and client code automatically.

Description

Workflow Changes:

• Added a GitHub Actions workflow named Validate OpenAPI Spec and Generated Client Code
  • Validates changes in openapi.yaml, server and client-generated code.
  • Automatically posts comments on pull requests when validation fails.
  • Removes sticky comments when validation passes.

Gradle Changes

• Added a new bootRunDev task to simplifies running the Spring Boot application in the dev profile
• Configured openApi Gradle plugin to set/use the openapi profile.
• Dynamically adds the H2 database dependency during the OpenAPI generation task (while generating the openapi yml file, the PostgreSQL connection is not necessary anymore).
• New task enforces an active Spring profile to be set before executing bootRun.

Application server config changes

• application-dev.yml added for local development
• application-openapi.yml added for openapi.yml generation task
• application.yml simplified for base usage

Testing Instructions

• Run ./gradlew bootRunDev to verify the dev profile works as intended.
• Execute ./gradlew generateOpenApiDocs to ensure OpenAPI specs are generated correctly.