docs: additions to systemd installation doc

[jason-lynch]

Summary

Adds sections to describe the limitations in the current release and how to uninstall the control plane. Also cleans up some of the formatting to comply with our documentation standards.

Testing

# these instructions depend on changes in my other branch
git checkout feat/switch-systemd-to-pgedge-patroni

# make sure that the dev-lima and dev environments are stopped
make dev-lima-reset
make dev-reset

# deploy a new VM from the dev-lima template
limactl start -y --name=rpm-test-1 lima/lima-template.yaml

# build a test RPM
make goreleaser-test-release

# ssh to the new machine
ssh -F ~/.lima/rpm-test-1/ssh.config lima-rpm-test-1

# follow the instructions from the doc, except instead of downloading the RPM,
# install the one for your architecture from
# <path to control plane project on your host machine>/dist/, e.g.
rpm -i /Users/jasonlynch/workspace/pgEdge/control-plane/dist/pgedge-control-plane_0.7.0-SNAPSHOT-24294c1f_linux_arm64.rpm

# when you're done, exit back to your host, stop the machine and delete it
limactl stop rpm-test-1
limactl delete rpm-test-1

Notes for Reviewers

The change to pgEdge Enterprise Postgres Patroni requires a small code change that I've made in #372.

PLAT-560

[coderabbitai]

📝 Walkthrough

Walkthrough

The systemd installation docs were revised: added a Limitations section, switched Patroni installation from pip to the pgedge-patroni RPM flow, clarified prerequisites/configuration (ports, POSTGRES_MAJOR_VERSION, data_dir, host_id, patroni_port), expanded cluster init/join steps with examples, and added uninstall procedures.

Changes

Cohort / File(s)

Summary

Systemd installation docs docs/installation/systemd.md

Comprehensive rewrite: added a Limitations section for systemd clusters; changed Patroni install from pip to pgedge-patroni RPMs and listed installed paths; standardized sudo on commands; renamed env var to POSTGRES_MAJOR_VERSION; clarified required ports and config keys (data_dir, host_id, patroni_port); expanded cluster init/join with an example DB creation API call and NOTE callouts (default host IDs, how to fetch host IDs); added new Uninstall section covering API-driven and manual removal steps including stopping systemd units and deleting per-instance data dirs.

Poem

🐇 I hop through docs both crisp and neat,

From pip to RPM I tap my feet.
With sudo steps and notes that gleam,
Clusters start, join, and leave the stream.
A rabbit's nibble on every seam.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'docs: additions to systemd installation doc' clearly reflects the main change—adding documentation sections to the systemd installation guide.
Description check	✅ Passed	The PR description includes a summary and testing steps with clear instructions, but is missing the Changes section, Checklist, and some optional details from the template.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch docs/PLAT-560/systemd-docs-additions

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[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

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[mmols]

Doc updates look good, pending QA running through them more in depth. I suggested one change to the preview note at the top of the doc.

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@docs/installation/systemd.md`:
- Around line 46-47: The two bullet descriptions for Etcd ports are reversed:
change the entry that currently states "Port 2379 uses TCP for Etcd peer
communication" to say "Port 2379 uses TCP for Etcd client communication" and
change the entry that currently states "Port 2380 uses TCP for Etcd client
communication" to say "Port 2380 uses TCP for Etcd peer communication" so that
port 2379 is documented as client and port 2380 as peer; update any adjacent
wording referencing these ports to match the corrected roles.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: b221be61-4a88-43f3-9714-92bcb99c97f2

📥 Commits

Reviewing files that changed from the base of the PR and between 1e081a8 and f38cbb7.

📒 Files selected for processing (1)

• docs/installation/systemd.md

[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

docs/installation/systemd.md (1)

62-62: ⚡ Quick win

Address markdownlint findings to meet the stated docs-formatting objective.

These changed lines still trigger markdownlint warnings (MD046 and MD028). Since this PR explicitly targets documentation standards cleanup, it’s worth resolving them in this pass.

Also applies to: 145-145, 151-151, 157-157, 198-198, 233-233, 246-246, 270-270, 276-276, 285-285, 291-291, 301-301, 317-317, 324-324, 336-336

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@docs/installation/systemd.md` at line 62, Fix markdownlint MD046/MD028 by
ensuring all fenced code blocks use a consistent fence style and have a blank
line separating them from preceding list items or paragraphs: replace any
inconsistent fences with triple backticks (```) and ensure the opening and
closing fences match and include the language tag (e.g., ```sh) consistently;
also add a single blank line before each fenced block when it follows a list
item or paragraph to satisfy MD028. Apply these changes to the occurrences
mentioned (the triple-backtick/code-block markers such as ```sh at the noted
locations).

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@docs/installation/systemd.md`:
- Around line 331-333: The docs currently imply the instance data path comes
from the control-plane config, but for systemd-managed PostgreSQL the path is
package-manager / service-derived (e.g.,
/var/lib/pgsql/<major_version>/<instance_id>); update the wording around
`/var/lib/pgsql/<major_version>/<instance_id>` to state the default is set by
the package/systemd unit and not the control-plane config, and instruct
operators to confirm the actual data directory by inspecting the PostgreSQL
systemd service/unit (or package documentation) or by checking the
PGDATA/data_directory setting in postgresql.conf before removing any files so
custom locations aren’t accidentally deleted.

---

Nitpick comments:
In `@docs/installation/systemd.md`:
- Line 62: Fix markdownlint MD046/MD028 by ensuring all fenced code blocks use a
consistent fence style and have a blank line separating them from preceding list
items or paragraphs: replace any inconsistent fences with triple backticks (```)
and ensure the opening and closing fences match and include the language tag
(e.g., ```sh) consistently; also add a single blank line before each fenced
block when it follows a list item or paragraph to satisfy MD028. Apply these
changes to the occurrences mentioned (the triple-backtick/code-block markers
such as ```sh at the noted locations).

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 3d0d0a95-40d2-467c-b452-f340ba1db6e2

📥 Commits

Reviewing files that changed from the base of the PR and between f38cbb7 and 007b891.

📒 Files selected for processing (1)

• docs/installation/systemd.md