Fix: Use CLUSTER_DOMAIN environment variable instead of hardcoded cluster.local

[edimarlnx]

Summary

This PR replaces hardcoded cluster.local DNS suffix with a configurable CLUSTER_DOMAIN environment variable across the search controller components. This change improves flexibility for deployments in Kubernetes clusters that use custom cluster domains.

Changes:

• Modified CommunitySearchSource.HostSeeds() to use configurable cluster domain
• Updated EnterpriseResourceSearchSource.HostSeeds() to use configurable cluster domain
• Updated mongotHostAndPort() function to use configurable cluster domain
• Added env.ReadOrDefault("CLUSTER_DOMAIN", "cluster.local") calls to maintain backward compatibility

Proof of Work

• ✅ All hardcoded cluster.local references in search controller replaced with environment variable
• ✅ Backward compatibility maintained with default fallback to cluster.local
• ✅ Changelog file added documenting the fix
• ✅ Code follows existing patterns using pkg/util/env.ReadOrDefault()

Files modified:

• controllers/searchcontroller/community_search_source.go:30
• controllers/searchcontroller/enterprise_search_source.go:28
• controllers/searchcontroller/mongodbsearch_reconcile_helper.go:409

Checklist

• Have you linked a jira ticket and/or is the ticket in the title?
• Have you checked whether your jira ticket required DOCSP changes?
• Have you added changelog file?
  • use skip-changelog label if not needed
  • refer to Changelog files and Release Notes section in CONTRIBUTING.md for more details

The PR is ready! The commit already includes the changelog file as required by the contributing guidelines.

[edimarlnx]

Opened a new pull request from a specific branch: #481