Add BOSH properties for Locket DB health check.

[klapkov]

Summary

Adds BOSH job properties to configure the Locket database health check feature implemented in cloudfoundry/locket#39

Resolves: #1105

New Properties:

• diego.locket.enable_db_health_check - Feature flag (default: false)
• diego.locket.health_check_interval - Check frequency (default: 10 seconds)
• diego.locket.health_check_timeout - Check timeout (default: 5 seconds)
• diego.locket.health_check_failure_threshold - Failures before restart (default: 3)

Related Work:

• Locket implementation: Add configurable database health check with automatic restart on failure locket#39
• BBS BOSH properties: Add bbs db health check config properties #1088
• BBS implementation: Add health check of database to kill bbs if the db is nonfunctional bbs#134

Test Results

Tested on dev landscape with Cloud Foundry deployment:

• ✅ Test 1: Default disabled, no behavior change
• ✅ Test 2: Properties correctly templated, health checks run every 10s
• ✅ Test 3: Detected database failure, auto-restart works
• ✅ Test 4: Timeout configuration works correctly
• ✅ Test 5: All property values applied correctly with time units

Deployment Example

instance_groups:
- name: diego-api
  jobs:
  - name: locket
    properties:
      diego:
        locket:
          enable_db_health_check: true
          health_check_interval: 10
          health_check_timeout: 5
          health_check_failure_threshold: 3

Backward Compatibility

Breaking Change? No

All properties have safe defaults and the feature is disabled by default. Operators can upgrade without manifest changes. Health check can be enabled after upgrade via configuration-only deployment.