Recommend/convert to use case-sensitive collation for MySQL/MSSQL (#28662)

Mainly for MySQL/MSSQL.

It is important for Gitea to use case-sensitive database charset
collation. If the database is using a case-insensitive collation, Gitea
will show startup error/warning messages, and show the errors/warnings
on the admin panel's Self-Check page.

Make `gitea doctor convert` work for MySQL to convert the collations of
database & tables & columns.

* Fix #28131

## ⚠️ BREAKING ⚠️

It is not quite breaking, but it's highly recommended to convert the
database&table&column to a consistent and case-sensitive collation.

routers/web/admin/admin.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	activities_model "code.gitea.io/gitea/models/activities"
+	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/modules/base"
 	"code.gitea.io/gitea/modules/context"
 	"code.gitea.io/gitea/modules/graceful"
@@ -27,6 +28,7 @@ import (
 
 const (
 	tplDashboard   base.TplName = "admin/dashboard"
+	tplSelfCheck   base.TplName = "admin/self_check"
 	tplCron        base.TplName = "admin/cron"
 	tplQueue       base.TplName = "admin/queue"
 	tplStacktrace  base.TplName = "admin/stacktrace"
@@ -172,6 +174,33 @@ func DashboardPost(ctx *context.Context) {
 	}
 }
 
+func SelfCheck(ctx *context.Context) {
+	ctx.Data["PageIsAdminSelfCheck"] = true
+	r, err := db.CheckCollationsDefaultEngine()
+	if err != nil {
+		ctx.Flash.Error(fmt.Sprintf("CheckCollationsDefaultEngine: %v", err), true)
+	}
+
+	if r != nil {
+		ctx.Data["DatabaseType"] = setting.Database.Type
+		ctx.Data["DatabaseCheckResult"] = r
+		hasProblem := false
+		if !r.CollationEquals(r.DatabaseCollation, r.ExpectedCollation) {
+			ctx.Data["DatabaseCheckCollationMismatch"] = true
+			hasProblem = true
+		}
+		if !r.IsCollationCaseSensitive(r.DatabaseCollation) {
+			ctx.Data["DatabaseCheckCollationCaseInsensitive"] = true
+			hasProblem = true
+		}
+		ctx.Data["DatabaseCheckInconsistentCollationColumns"] = r.InconsistentCollationColumns
+		hasProblem = hasProblem || len(r.InconsistentCollationColumns) > 0
+
+		ctx.Data["DatabaseCheckHasProblems"] = hasProblem
+	}
+	ctx.HTML(http.StatusOK, tplSelfCheck)
+}
+
 func CronTasks(ctx *context.Context) {
 	ctx.Data["Title"] = ctx.Tr("admin.monitor.cron")
 	ctx.Data["PageIsAdminMonitorCron"] = true

routers/web/web.go

@@ -678,6 +678,8 @@ func registerRoutes(m *web.Route) {
 		m.Get("", admin.Dashboard)
 		m.Post("", web.Bind(forms.AdminDashboardForm{}), admin.DashboardPost)
 
+		m.Get("/self_check", admin.SelfCheck)
+
 		m.Group("/config", func() {
 			m.Get("", admin.Config)
 			m.Post("", admin.ChangeConfig)