gateway-api: Fix double slash when trying to strip path prefix

[nxy7]

• Merge slashes in URI path
• Gateway to CEC translation fix

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Stripping path prefix leads to double slashes in URI path. To fix that I've enabled envoy merge_slashes option.

Fixes: #28270

Fix: Gateway API double slash while stripping path prefix

[maintainer-s-little-helper]

Commit e629c88f15ebe94171352dd68f4dc68049252a97 does not match "(?m)^Signed-off-by:".

Please follow instructions provided in https://docs.cilium.io/en/stable/contributing/development/contributing_guide/#developer-s-certificate-of-origin

[nxy7]

Okay, so I found the root cause of the issue. It is indeed envoy problem. For whatever reason merging slashes only works between path segments (it seems like they are first merging slashes and only then doing path rewrites).
Also, we cannot pass empty rewritePrefix as that's ignored by envoy. The only solution to this issue seems to be using regexp rewrite, that can in fact accept empty substitution string.
I've tested ebb5dce and it strips prefixes correctly. To do that I've had to pass *model.HTTPRoute to getRouteAction and pathPrefixMutation because regexp in pathPrefixMutation needs to be aware of path that it's supposed to substitute.
What do you think about that solution @sayboras ?

[maintainer-s-little-helper]

Commit 2185aa43bb39751c1f54b7829ca6d8b38b5d36f7 does not match "(?m)^Signed-off-by:".

Please follow instructions provided in https://docs.cilium.io/en/stable/contributing/development/contributing_guide/#developer-s-certificate-of-origin

[lmb]

@sayboras can you take a look please?

[lmb]

@nxy7 seems like your PR includes a merge of the main branch, please rebase your changes on top of main instead. Also try squashing into as few commits as possible please.

[nxy7]

I've kind of made a mess with this git history (sorry for that, I'm not very good at using git), but it should be good now. I've reduced commits to 3 and rebased all changes on top of main.

[sayboras]

Thanks for your PR.

Please find below my comments. Also, can you help to merge all commits into one as we are using rebase and merge strategy to keep main history clean.

[nxy7]

I've applied all your suggestions @sayboras, hope it's okay now.

[sayboras]

/test

[sayboras]

Thanks and LGTM ✔️

[sayboras]

I tried to resolve the conflict and merge this in, however, it seems like I didn't have permission to push to your fork.

Can you help to resolve the conflict? It should be quite straightforward like the below main...sayboras:cilium:tam/resolve-conflict-28294

[nxy7]

Done :-)

[sayboras]

/test

[ti-mo]

/test

[sayboras]

Thanks a lot for your help from analysing to sending the patch 🥇