Allow multiple cookie domains to be specified (#412)

* Allow multiple cookie domains to be specified

* Use X-Forwarded-Host, if it exists, when selecting cookie domain

* Perform cookie domain sorting in config validation phase

* Extract get domain cookies to a single function

* Update pkg/cookies/cookies.go

Co-Authored-By: Joel Speed <Joel.speed@hotmail.co.uk>

* Update changelog

Co-authored-by: Marcos Lilljedahl <marcosnils@gmail.com>
Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

pkg/sessions/session_store_test.go

@@ -63,7 +63,11 @@ var _ = Describe("NewSessionStore", func() {
 
 			It("have the correct domain set", func() {
 				for _, cookie := range cookies {
-					Expect(cookie.Domain).To(Equal(cookieOpts.CookieDomain))
+					specifiedDomain := ""
+					if len(cookieOpts.CookieDomains) > 0 {
+						specifiedDomain = cookieOpts.CookieDomains[0]
+					}
+					Expect(cookie.Domain).To(Equal(specifiedDomain))
 				}
 			})
 
@@ -343,7 +347,7 @@ var _ = Describe("NewSessionStore", func() {
 					CookieRefresh:  time.Duration(2) * time.Hour,
 					CookieSecure:   false,
 					CookieHTTPOnly: false,
-					CookieDomain:   "example.com",
+					CookieDomains:  []string{"example.com"},
 					CookieSameSite: "strict",
 				}