api: add extension configuration to EnvoyGateway

[haq204]

Companion to #1074. This adds the configuration necessary in EnvoyGateway to register an extension

Relates to #20

[codecov-commenter]

Codecov Report

Merging #1163 (5381bb9) into main (6936ac7) will increase coverage by 0.10%.
The diff coverage is 68.42%.

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@@            Coverage Diff             @@
##             main    #1163      +/-   ##
==========================================
+ Coverage   63.04%   63.14%   +0.10%     
==========================================
  Files          79       79              
  Lines        9744     9763      +19     
==========================================
+ Hits         6143     6165      +22     
+ Misses       3185     3182       -3     
  Partials      416      416              

Impacted Files	Coverage Δ
internal/envoygateway/config/config.go	80.35% <68.42%> (-6.13%)	⬇️

... and 2 files with indirect coverage changes

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[Alice-Lilith]

Lgtm, thanks 🙂

[arkodg]

LGTM, thanks for addressing all the comments, hoping this API unlocks a wider set of use cases for the ecosystem !

[arkodg]

ptal @youngnick @skriss @zirain @Xunzhuo

[Xunzhuo]

Looks good

[zirain]

just one small question, should Extension be a slice?

[arkodg]

just one small question, should Extension be a slice?

good point, either we make it Extensions and add a runtime check of 1 or deprecate this field in favor of Extensions when we support multiple

[zirain]

ok, let's review that later, LGTM for now.

[haq204]

As stated in #1074 we made the decision to not support multiple extensions at the same time:

• Too difficult to make sure extensions wouldn't step on each other's toes or conflict
• Realistically few people would be running multiple extensions at the same time. Smaller extensions to Envoy Gateway can be accommodated later via Allow users to configure xDS resources #24 and WASM Plugin Design and Implementation #71 which can co-exist with this form of extensions

[haq204]

just one small question, should Extension be a slice?

good point, either we make it Extensions and add a runtime check of 1 or deprecate this field in favor of Extensions when we support multiple

I went back and forth on whether this should be a slice given that we would not be supporting more than one extension at this time due to the reasons above.

Only way I see it is if there is a path forward to supporting multiple extensions which I don't think we would. If we did ever support multiple extensions then yes I would favor creating anew Extensions field and deprecate Extension

[zirain]

@arkodg should get #1074 merged?

[arkodg]

@arkodg should get #1074 merged?

we discussed this in the community meeting, and @AliceProxy and @haq204 mentioned they will raise some PRs for the Hooks API to make sure it is in line with the design doc contents