fix: revert using cookies package to fix cookie headers handling

[rclement]

PR #327 introduced a significant increase of vendors bundle size, as reported in issue #330.

The root cause was the replacement of the cookie package with the cookies one, while fixing a severe bug in Set-Cookie headers handling for the SSR language redirection cookie.

This PR reverts to using the cookie package but performs manually the Set-Cookie header handling, exactly the way the cookies package does (i.e. no previous cookie, a single cookie or a list of cookies).

Hopefully, this one will do the trick!

[codecov]

Codecov Report

Merging #332 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #332   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           2      2           
  Lines           6      6           
=====================================
  Hits            6      6

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[rchl]

LGTM

[rchl]

I've squashed this with your previous change locally to see changes relative to pre-cookies-package change and got this simple diff:

diff --git a/src/plugins/main.js b/src/plugins/main.js
index d916954..35f3b34 100644
--- a/src/plugins/main.js
+++ b/src/plugins/main.js
@@ -66,11 +66,18 @@ export default async (context) => {
         path: '/'
       })
     } else if (res) {
+      let headers = res.getHeader('Set-Cookie') || []
+      if (typeof headers == 'string') {
+        headers = [headers]
+      }
+
       const redirectCookie = Cookie.serialize(cookieKey, locale, {
         expires: new Date(date.setDate(date.getDate() + 365)),
         path: '/'
       })
-      res.setHeader('Set-Cookie', redirectCookie)
+      headers.push(redirectCookie)
+
+      res.setHeader('Set-Cookie', headers)
     }
   }

Makes it easier to evaluate changes.

[paulgv]

Awesome! Thank you for the PR @rclement! And thank you for posting the diff @rchl! LGTM.