Apply Spring Boot connection validation settings to HttpClient

[vadimturkov]

The change ensures time-to-live and validate-after-inactivity are merged correctly and applied to the underlying ConnectionConfig, including the default configuration for the Spring Boot starter.

Description

This PR fixes the Spring Boot auto-configuration for Apache HttpClient connections by ensuring the connection lifecycle settings are correctly merged and applied.

The update adds validate-after-inactivity to the Spring Boot properties model, keeps the default value consistent with the starter defaults, and ensures client-specific values override the default configuration as expected. It also wires both time-to-live and validate-after-inactivity into the underlying ConnectionConfig used by the pooled HttpClient.

In addition, the documentation was updated to describe the new property and regression tests were added to cover both defaulting and configuration behavior.

Motivation and Context

The Spring Boot auto-configured HttpClient was missing part of the connection configuration. In particular, the inactivity validation setting was not being merged or applied, which could allow stale pooled connections to remain active longer than intended.

This change ensures that connection lifetime and inactivity validation are configured consistently for Riptide clients using the Spring Boot starter.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.

[fatroom]

👍

[vadimturkov]

👍