fix(helm-prereqs): make Patroni synchronous mode values-driven

[jabdulvahid]

Hardcoded synchronous_mode_strict deadlocks single-instance postgres clusters: with no standby to acknowledge commits, all writes block -- including the operator's own CREATE DATABASE, so the chart's databases are never created. Expose it as postgresql.synchronousMode (default true, production behavior unchanged).

The default lives in values.yaml rather than '| default true' in the template: Go templates treat an explicit false as empty, which would silently coerce it back to true.

Fixes #5095

Related issues

Type of Change

• Add - New feature or capability
• Change - Changes in existing functionality
• Fix - Bug fixes
• Remove - Removed features or deprecated functionality
• Internal - Internal changes (refactoring, tests, docs, etc.)

Breaking Changes

• This PR contains breaking changes

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• No testing required (docs, internal refactor, etc.)

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Reviewing files that changed from the base of the PR and between 1ec08ca and 412652b.

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• helm-prereqs/templates/postgresql.yaml
• helm-prereqs/values.yaml

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Summary by CodeRabbit

• New Features
  • PostgreSQL synchronous replication can now be configured through deployment values.
  • Synchronous replication is enabled by default, with settings documented for single-instance development environments.

Walkthrough

The Helm chart adds postgresql.synchronousMode, defaults it to true, and uses it for Patroni synchronous replication settings. Deployments with one PostgreSQL instance can set it to false.

Changes

Patroni synchronous mode configuration

Layer / File(s)	Summary
Values-driven synchronous mode helm-prereqs/values.yaml, helm-prereqs/templates/postgresql.yaml	The chart defines postgresql.synchronousMode as true. The Patroni synchronous_mode and synchronous_mode_strict settings use this value. The comments document setting it to false for single-instance clusters.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 41265

The change makes Patroni synchronous mode configurable while preserving the existing production default, with no actionable merge-blocking risk remaining after normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the chart fix: making Patroni synchronous mode values-driven.
Description check	✅ Passed	The description explains the single-instance deadlock, configuration change, default behavior, and linked issue.
Linked Issues check	✅ Passed	The changes satisfy issue #5095 by templating both Patroni synchronous settings and defining the default in values.yaml.
Out of Scope Changes check	✅ Passed	All changes are limited to the requested Patroni configuration and its chart values documentation.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[shayan1995]

LGTM