Add HTTP Cache support to http_ng

[mikz]

Using Cache-Control: private the http client
should be able to cache responses and use the cache
on repeated calls

Good read: https://tools.ietf.org/html/rfc7234

You can use it like:

local cache_store = require('resty.http_ng.cache_store')
local resty_backend = require('resty.http_ng.backend.resty')
local cache_backend = require('resty.http_ng.backend.cache')

-- cache_backend.new(resty_backend) would use default cache store, but you can customise its size
local backend = cache_backend.new(resty_backend, { cache_store = cache_store.new(100) })
local http_client = http_ng.new({ backend = backend })

[octobot]

	2 Warnings
⚠️	PR is classed as Work in Progress
⚠️	Big PR

Generated by 🚫 Danger

[macejmic]

what's the difference between : and . ?

[mikz]

Hah! : is syntactic sugar for passing self.

So these are the same code:

object:method(param)
object.method(object, param)

This works in the function definition too:

function _M.method(self, param)
end

function _M:method(param)
end

Passing self It is the only way how a function can know about the object being called on. Like instance method. Otherwise it does not really have any state other than a closure.