refactor!: move go-chi/session into Gitea (#39504)

The `gitea.com/go-chi/session` package only exists for Gitea, so it
moves into `modules/session` to fix its bugs directly. Fixes the flake
in
https://github.com/go-gitea/gitea/actions/runs/36726154500/job/109923538400.

- Sessions are only written back when changed, so a read-only request
can't revert a concurrent change or restore a logged-out session, like
https://github.com/go-macaron/session/commit/ae808a4a4660c802965c834299ab08f167effd12
- The session cookie is only set once a session holds data
- Every backend refreshes the expiry on load and file sessions are
written atomically
- Also fix  https://github.com/go-gitea/gitea/issues/36176

## ⚠️ BREAKING ⚠️

* the `mysql`, `postgres`, `couchbase` and `memcache` session providers
are removed, use `file`, `db` or `redis` instead
* login-related cookies are renamed to `gitea_session` and
`gitea_remember`, if you'd like to use the old names, set `COOKIE_NAME`
and `COOKIE_REMEMBER_NAME` in app.ini

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/setting/session.go

@@ -4,19 +4,17 @@
 package setting
 
 import (
+	"cmp"
 	"net/http"
 	"path/filepath"
 	"strings"
 
-	"gitea.dev/modules/json"
-	"gitea.dev/modules/log"
 	"gitea.dev/modules/util"
 )
 
 // SessionConfig defines Session settings
 var SessionConfig = struct {
-	OriginalProvider string
-	Provider         string
+	Provider string
 	// Provider configuration, it's corresponding to provider.
 	ProviderConfig string
 	// Cookie name to save session ID. Default is "MacaronSession".
@@ -34,7 +32,8 @@ var SessionConfig = struct {
 	// SameSite declares if your cookie should be restricted to a first-party or same-site context. Valid strings are "none", "lax", "strict". Default is "lax"
 	SameSite http.SameSite
 }{
-	CookieName:  "i_like_gitea",
+	Provider:    "memory", // the "Install" page doesn't load the [session] config
+	CookieName:  "gitea_session",
 	Gclifetime:  86400,
 	Maxlifetime: 86400,
 	SameSite:    http.SameSiteLaxMode,
@@ -42,7 +41,7 @@ var SessionConfig = struct {
 
 func loadSessionFrom(rootCfg ConfigProvider) {
 	sec := rootCfg.Section("session")
-	SessionConfig.Provider = sec.Key("PROVIDER").In("file", []string{"memory", "file", "redis", "mysql", "postgres", "couchbase", "memcache", "db"})
+	SessionConfig.Provider = sec.Key("PROVIDER").MustString("file")
 
 	switch SessionConfig.Provider {
 	case "redis":
@@ -59,12 +58,12 @@ func loadSessionFrom(rootCfg ConfigProvider) {
 		SessionConfig.ProviderConfig = sec.Key("PROVIDER_CONFIG").String()
 	}
 
-	SessionConfig.CookieName = sec.Key("COOKIE_NAME").MustString("i_like_gitea")
-	// HINT: INSTALL-PAGE-COOKIE-INIT: the cookie system is not properly initialized on the Install page, so there is no CookiePath
+	SessionConfig.CookieName = sec.Key("COOKIE_NAME").MustString("gitea_session")
+	// HINT: INSTALL-PAGE-COOKIE-INIT: the cookie system is not properly initialized on the "Install" page, so there is no CookiePath
 	SessionConfig.CookiePath = util.IfZero(AppSubURL, "/")
 	SessionConfig.Secure = sec.Key("COOKIE_SECURE").MustBool(strings.HasPrefix(strings.ToLower(AppURL), "https://"))
-	SessionConfig.Gclifetime = sec.Key("GC_INTERVAL_TIME").MustInt64(86400)
-	SessionConfig.Maxlifetime = sec.Key("SESSION_LIFE_TIME").MustInt64(86400)
+	SessionConfig.Gclifetime = cmp.Or(max(sec.Key("GC_INTERVAL_TIME").MustInt64(86400), 0), 3600)
+	SessionConfig.Maxlifetime = cmp.Or(max(sec.Key("SESSION_LIFE_TIME").MustInt64(86400), 0), SessionConfig.Gclifetime)
 	SessionConfig.Domain = sec.Key("DOMAIN").String()
 	samesiteString := sec.Key("SAME_SITE").In("lax", []string{"none", "lax", "strict"})
 	switch strings.ToLower(samesiteString) {
@@ -75,11 +74,4 @@ func loadSessionFrom(rootCfg ConfigProvider) {
 	default:
 		SessionConfig.SameSite = http.SameSiteLaxMode
 	}
-	shadowConfig, err := json.Marshal(SessionConfig)
-	if err != nil {
-		log.Fatal("Can't shadow session config: %v", err)
-	}
-	SessionConfig.ProviderConfig = string(shadowConfig)
-	SessionConfig.OriginalProvider = SessionConfig.Provider
-	SessionConfig.Provider = "VirtualSession"
 }