user-guide: add gateway-failover documentation

[Fredi-raspall]

Closes: #248
Unsure if this closes #249

[github-actions]

🚀 Deployed on https://preview-259--hedgehog-docs.netlify.app

[Copilot]

Pull request overview

This PR extends the user guide to document gateway redundancy/fail-over behavior and integrates the new material into the navigation and existing gateway docs. It also slightly refines existing gateway-related titles to better reflect their scope.

Changes:

• Add a dedicated “Gateway fail-over and redundancy” user-guide page explaining gateway groups, traffic mapping, and fail-over behavior.
• Link the new page from the overview and the .pages navigation under a new “Gateway” section.
• Retitle the main gateway and gateway-add docs to “Gateway overview” and “Adding Gateways to the fabric” for clearer context.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
docs/user-guide/overview.md	Adds a TOC entry pointing to the new gateway-failover documentation so users can discover redundancy guidance.
docs/user-guide/gateway.md	Renames the main heading to “Gateway overview” to clarify that this page introduces gateway concepts now complemented by a separate fail-over page.
docs/user-guide/gateway-failover.md	Introduces detailed documentation for gateway redundancy, gateway groups, traffic mapping, and fail-over behavior, including configuration snippets and design rationale.
docs/user-guide/gateway-add.md	Updates the title to “Adding Gateways to the fabric” to align with a more general multi-gateway deployment story.
docs/user-guide/.pages	Groups gateway-related docs under a “Gateway” nav section and includes the new fail-over page, improving navigation around gateway topics.

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[qmonnet]

Great document!

I'm usually picky with the style in the docs (Logan knows something about it), so I've got tons of nitpicks, but nothing major.

I'd also wrap the text on 80-character lines as I find it easier to diff and work with smaller lines, although I'm not sure we have a consensus about that.

One comment would be to remain careful with the number of admonitions (!!! note) in the document. It's good to have a few ones to insert visual pauses in long sections, but having too many ones may break the flow. You have quite a number of nots, and I think some of them could be regular paragraphs and it would help with overall readability.

[pau-hedgehog]

I come to this PR to say that you could put a diagram on it: ;)

I could work on representing the gateway group if you need it

[Fredi-raspall]

I come to this PR to say that you could put a diagram on it: ;)
I could work on representing the gateway group if you need it

Hey Pau. I'm fine adding a diagram. However I am not sure if it will help too much if:

• we cannot represent VPCs
• How would you represent groups?

We could add some representation, but it will mostly need to be manual?

[pau-hedgehog]

I come to this PR to say that you could put a diagram on it: ;)
I could work on representing the gateway group if you need it

Hey Pau. I'm fine adding a diagram. However I am not sure if it will help too much if:

• we cannot represent VPCs
• How would you represent groups?

We could add some representation, but it will mostly need to be manual?

On fabricator master we can represent VPCs already by querying a running Fabric (hhfab vlab diagram --live):

• How would you represent groups?

I was thinking something similar to ESLAG groups to enclose gateways in a dashed rectangle. Shouldn't be too difficult. But I don't want to add noise to this review. We can address it some other time

[Fredi-raspall]

I come to this PR to say that you could put a diagram on it: ;)
I could work on representing the gateway group if you need it

Hey Pau. I'm fine adding a diagram. However I am not sure if it will help too much if:

• we cannot represent VPCs
• How would you represent groups?

We could add some representation, but it will mostly need to be manual?

On fabricator master we can represent VPCs already by querying a running Fabric (hhfab vlab diagram --live):

• How would you represent groups?

I was thinking something similar to ESLAG groups to enclose gateways in a dashed rectangle. Shouldn't be too difficult. But I don't want to add noise to this review. We can address it some other time

Nice! I'm fine with adding it if it helps to understand the feature. Can be now or later.

[qmonnet]

Looks OK from my side, thanks!

[Frostman]

It looks okay other then the primary gateway selection - that have to be fixed but docs could be updated later

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

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[qmonnet]

This one has been pending for a long time. I think it's ready to go, let's merge it. We can improve it in a follow-up PR if necessary (I'm still not convinced by the inline, right-hand-side notes aside the YAML boxes, for example).

Thanks Fredi!

[qmonnet]

And what's the matter with the DCO check not running, now? 🤔