Avoid importing `modules/web/middleware` in `modules/session` (#30584)

Related to #30375.

It doesn't make sense to import `modules/web/middleware` and
`modules/setting` in `modules/web/session` since the last one is more
low-level.

And it looks like a workaround to call `DeleteLegacySiteCookie` in
`RegenerateSession`, so maybe we could reverse the importing by
registering hook functions.

modules/session/store.go

@@ -6,9 +6,6 @@ package session
 import (
 	"net/http"
 
-	"code.gitea.io/gitea/modules/setting"
-	"code.gitea.io/gitea/modules/web/middleware"
-
 	"gitea.com/go-chi/session"
 )
 
@@ -21,10 +18,12 @@ type Store interface {
 
 // RegenerateSession regenerates the underlying session and returns the new store
 func RegenerateSession(resp http.ResponseWriter, req *http.Request) (Store, error) {
-	// Ensure that a cookie with a trailing slash does not take precedence over
-	// the cookie written by the middleware.
-	middleware.DeleteLegacySiteCookie(resp, setting.SessionConfig.CookieName)
-
+	for _, f := range BeforeRegenerateSession {
+		f(resp, req)
+	}
 	s, err := session.RegenerateSession(resp, req)
 	return s, err
 }
+
+// BeforeRegenerateSession is a list of functions that are called before a session is regenerated.
+var BeforeRegenerateSession []func(http.ResponseWriter, *http.Request)

modules/web/middleware/cookie.go

@@ -9,6 +9,7 @@ import (
 	"net/url"
 	"strings"
 
+	"code.gitea.io/gitea/modules/session"
 	"code.gitea.io/gitea/modules/setting"
 )
 
@@ -48,12 +49,12 @@ func SetSiteCookie(resp http.ResponseWriter, name, value string, maxAge int) {
 	// Previous versions would use a cookie path with a trailing /.
 	// These are more specific than cookies without a trailing /, so
 	// we need to delete these if they exist.
-	DeleteLegacySiteCookie(resp, name)
+	deleteLegacySiteCookie(resp, name)
 }
 
-// DeleteLegacySiteCookie deletes the cookie with the given name at the cookie
+// deleteLegacySiteCookie deletes the cookie with the given name at the cookie
 // path with a trailing /, which would unintentionally override the cookie.
-func DeleteLegacySiteCookie(resp http.ResponseWriter, name string) {
+func deleteLegacySiteCookie(resp http.ResponseWriter, name string) {
 	if setting.SessionConfig.CookiePath == "" || strings.HasSuffix(setting.SessionConfig.CookiePath, "/") {
 		// If the cookie path ends with /, no legacy cookies will take
 		// precedence, so do nothing.  The exception is that cookies with no
@@ -74,3 +75,11 @@ func DeleteLegacySiteCookie(resp http.ResponseWriter, name string) {
 	}
 	resp.Header().Add("Set-Cookie", cookie.String())
 }
+
+func init() {
+	session.BeforeRegenerateSession = append(session.BeforeRegenerateSession, func(resp http.ResponseWriter, _ *http.Request) {
+		// Ensure that a cookie with a trailing slash does not take precedence over
+		// the cookie written by the middleware.
+		deleteLegacySiteCookie(resp, setting.SessionConfig.CookieName)
+	})
+}