feat(serverless) bundle serverless function plugins

[nijikokun]

Bundles serverless function plugins into Kong CE.

Caveats

• pre-function runs before zipkin, it is advisable to use post-function when using zipkin for accurate metric reporting.
  • If we want to change this behavior, I would advise that we raise the priority on the zipkin plugin to math.huge, and set the pre-function value close nearby to stay consistent with documentation.

[nijikokun]

@thibaultcha that is correct, I have made a note of this in the PR description.

[thibaultcha]

@nijikokun My comment was made on the commit and pre-dated the PR - hid it as "obsolete".

[coopr]

Is there any uncertainty as to "if we want to change this"? I can't guess why we would not want to change this - it seems necessary that Zipkin run before pre-function for the reason stated.

[nijikokun]

@coopr that's what the purpose of that text is for, to decide such. I'm not sure whether it is necessary. There are two plugins (pre / post), one can run after Zipkin (post), one (pre) explicitly states it runs before all others.

Therefore, if you want to use a function and zipkin, you can use post.

[coopr]

Ah, thanks for the clarification.

In my opinion, if you are running Zipkin (or, really, anything else that monitors Kong's execution of Kong's code), you'd want it to start running as early as possible.

Running Zipkin before pre-function can't, as far as I understand, affect the execution of the pre-function in any way.