Allow ipv4-only setups, or at least allow specifying env values for the documentdb-owned pods

[AntonOfTheWoods]

Describe the bug

2026-05-17T08:31:32.707816Z  INFO documentdb_gateway_core::postgres::conn_mgmt::pool_manager: Performing the cleanup of unused pools event_id=2002  thread 'main' (1) panicked at documentdb_gateway/src/main.rs:104:10: called `Result::unwrap()` on an `Err` value: IoError { error: Os { code: 97, kind: Uncategorized, message: "Address family not supported by protocol" }, backtrace: <disabled> } note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

To Reproduce
Steps to reproduce the behavior:

1. Install Document DB Operator following the docs on a kubernetes with ipv6 disabled

Expected behavior
It should work

Kubernetes Environment (please complete the following information):

• DocumentDB Operator Version [e.g. 123]
  0.110.0
• Kubernetes Version [e.g. 23]
  1.36.0
• Kubernetes Environment [e.g. AKS, KIND]
  k3s
• Cert Bot Version [e.g. 123]
  v1.20.2
• CNPG Version (if not installed by our helm chart) [e.g. 123]
  0.28.1

Additional context
Add any other context about the problem here.

[documentdb-triage-tool]

🤖 Auto-triaged by documentdb-triage-tool.

Applied: go, bug
Project fields suggested: Component controllers · Priority P1 · Effort M · Status In Progress
Confidence: 0.75 (llm)

Reasoning

LLM: A panic (unwrap on Err) in the gateway's main.rs causes a crash on IPv4-only Kubernetes clusters due to an unsupported IPv6 address family, making the operator non-functional in a common deployment scenario.

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[documentdb-triage-tool]

👋 @hossain-rayhan — this issue has been assigned for 15 days with no activity. Is it still in progress? If you've made progress, please leave a quick update. Otherwise it'll be flagged for re-assignment at the next triage meeting.