feat: require explicit environment and add Spring Boot starter module

[hmaheshwari-godaddy]

Summary

• Breaking: AnsConfiguration.builder().build() now throws IllegalStateException if .environment() is not set. This prevents production deployments from silently using OTE.
• New module: ans-sdk-spring-boot-starter provides Spring Boot auto-configuration, binding ans.* properties to SDK beans (AnsConfiguration, RegistrationClient, DiscoveryClient).
• Example: Spring Boot app under ans-sdk-spring-boot-starter/examples/spring-boot-app/ demonstrating injected SDK usage.

Changes

Required environment (feat!)

• AnsConfiguration.Builder.environment default changed from Environment.OTE to null
• build() validates that environment is explicitly set
• All downstream tests updated to pass .environment(Environment.OTE)

Spring Boot starter (feat)

• AnsProperties — @ConfigurationProperties(prefix = "ans") with environment, credentials, timeouts, retries
• AnsAutoConfiguration — creates AnsCredentialsProvider, AnsConfiguration, RegistrationClient, DiscoveryClient beans
• Supports credential types: jwt, api-key, environment
• All beans use @ConditionalOnMissingBean for user overrides
• 13 auto-configuration tests using ApplicationContextRunner
• Example Spring Boot app with REST controller

Test plan

• ./gradlew build passes (89 tasks, all green)
• Checkstyle zero warnings
• Auto-configuration tests cover: all credential types, missing fields, custom timeouts, disabled flag, user bean overrides
• Example app compiles and produces bootJar

[jhateley-godaddy]

LGTM

[jhateley-godaddy]

LGTM