Cookie encode throw exception in case of empty secret

[kaushik143]

Describe the bug
Cookie encode throw exception in case of empty secret

To Reproduce
Steps to reproduce the behavior:

1. Go to 'CookieSpec'
2. Change the cookies gen function to have only an empty secret

def cookies: Gen[Random with Sized, Cookie] = for {
  name     <- Gen.anyString
  content  <- Gen.anyString
  expires  <- Gen.option(Gen.anyInstant)
  domain   <- Gen.option(Gen.anyString)
  path     <- Gen.option(path)
  secure   <- Gen.boolean
  httpOnly <- Gen.boolean
  maxAge   <- Gen.option(Gen.anyLong)
  sameSite <- Gen.option(Gen.fromIterable(List(Cookie.SameSite.Strict, Cookie.SameSite.Lax)))
  secret   <- Gen.option(Gen.fromIterable(List("")))
} yield Cookie(name, content, expires, domain, path, secure, httpOnly, maxAge, sameSite, secret)

3. Run CookieSpec
4. See an error

java.lang.IllegalArgumentException: Empty key
at java.base/javax.crypto.spec.SecretKeySpec.(SecretKeySpec.java:110)

Expected behaviour
Encode shouldn't throw an exception

[dhyanpatel]

I'd like to take a shot at this!