fix(core): response phase skips header.before

[StarlightIbuki]

This causes some of the header handlings to be skipped.

Full changelog:

runloop.lua: moving the header phase before and after handlers and changing the way to get status in before handler
init.lua: adjust the ordering of handlers and set status (send headers).

Fix #10031

[bungle]

As discussed offline, I feel the right fix would be to change this:
https://github.com/Kong/kong/blob/master/kong/runloop/handler.lua#L1727

to

header[upstream_status_header] = ctx.buffered_status or tonumber(sub(var.upstream_status or "", -3))

[StarlightIbuki]

As discussed offline, I feel the right fix would be to change this: https://github.com/Kong/kong/blob/master/kong/runloop/handler.lua#L1727

to

header[upstream_status_header] = ctx.buffered_status or tonumber(sub(var.upstream_status or "", -3))

Does this work the same way:

      local upstream_status = ctx.buffered_status or var.upstream_status
      header[upstream_status_header] = tostring(tonumber(sub(upstream_status or "", -3)))

[bungle]

As discussed offline, I feel the right fix would be to change this: https://github.com/Kong/kong/blob/master/kong/runloop/handler.lua#L1727
to

header[upstream_status_header] = ctx.buffered_status or tonumber(sub(var.upstream_status or "", -3))

Does this work the same way:

      local upstream_status = ctx.buffered_status or var.upstream_status
      header[upstream_status_header] = tostring(tonumber(sub(upstream_status or "", -3)))

I think not. There is only possible multiple status codes on var, as it collects all status codes (from possible retries with balancer), but i think just one code in ctx that is read from location capture res.status.

[StarlightIbuki]

I think not. There is only possible multiple status codes on var, as it collects all status codes (from possible retries with balancer), but i think just one code in ctx that is read from location capture res.status.

I've updated the fix according to your comment.

[bungle]

I see you added tostring here. Not sure why. Perhaps then the tonumber above is unwanted. That is now it can set header to "nil". Not sure can it happen but still. Perhaps just remove the tostring?

[StarlightIbuki]

Removing. I was trying to eliminate a warning.