fix(http): Allow relative redirect on https (#395)

Location header can now be relative: https://httpwg.org/specs/rfc9110.html#field.location

src/http.lua

@@ -300,6 +300,8 @@ local function shouldredirect(reqt, code, headers)
     if not location then return false end
     location = string.gsub(location, "%s", "")
     if location == "" then return false end
+    -- the RFC says the redirect URL may be relative
+    location = url.absolute(reqt.url, location)
     local scheme = url.parse(location).scheme
     if scheme and (not SCHEMES[scheme]) then return false end
     -- avoid https downgrades
@@ -323,8 +325,7 @@ end
 local trequest, tredirect
 
 --[[local]] function tredirect(reqt, location)
-    -- the RFC says the redirect URL has to be absolute, but some
-    -- servers do not respect that
+    -- the RFC says the redirect URL may be relative
     local newurl = url.absolute(reqt.url, location)
     -- if switching schemes, reset port and create function
     if url.parse(newurl).scheme ~= reqt.scheme then