ngx.req.set_header(key, value ) in kong plugin should throw error for BWS ("bad" whitespace) in header key

Current Behavior

Adding header ngx.req.set_header("X-cnn-Service ", "") to a plugin is causing the request to throw HTTP 400 error due to the additional trailing whitespace in header's Key.
reference- field-parsing according to rfc7230 No whitespace is allowed between the header field-name and colon .
Due to a small leading/trailing whitespace mistake , much of the developers time is wasted to find this issue .

Expected Behavior

Two ideas can be proposed

1. Trim the leading/trailing whitespace of the header before plugin execution.
2. Log the error , that plugin execution failed for the request due to invalid header

Steps To Reproduce

Create a Plugin with the following in access.lua
`
local BasePlugin = require "kong.plugins.base_plugin"
local priorities = require "kong.plugins.priorities"

local plugin_name = "headers-plugin"

local KongHeadersHandler = BasePlugin:extend()

function KongHeadersHandler:new()
   KongHeadersHandler.super.new(self, plugin_name)
end

function KongHeadersHandler:access(conf)
  KongHeadersHandler.super.access(self)
  ngx.req.set_header("X-cnn-Service ", "")
end

KongHeadersHandler.PRIORITY = priorities[plugin_name]
KongHeadersHandler.VERSION = "0.0.1"

return KongHeadersHandler`

kong version 1.1.2
lua version Lua 5.1.4
LuaJIT 2.1.0-beta3
nginx version: openresty/1.13.6.2
LuaRocks main command-line interface /opt/kong/luajit/bin/luarocks 3.2.1

For ngx.header also it should trim white space or throw error instead of sending invalid header

example

header_filter_by_lua_block {
                ngx.header.Foo = "blah"
                ngx.header["name "] = 'X-12345'
            }

output

< Connection: keep-alive
< Foo: blah
< name%20: X-12345

Start by reproducing the trailing-space cases at ngx.req.set_header in the plugin's access.lua and at ngx.header in header_filter_by_lua_block. Read the handling behind these entry points and compare the observed HTTP 400 or encoded header output with RFC 7230; done means the intended invalid-header behavior is defined and covered for both APIs.