Use db.Find instead of writing methods for every object (#28084)

For those simple objects, it's unnecessary to write the find and count
methods again and again.

routers/web/admin/applications.go

@@ -8,6 +8,7 @@ import (
 	"net/http"
 
 	"code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/modules/base"
 	"code.gitea.io/gitea/modules/context"
 	"code.gitea.io/gitea/modules/setting"
@@ -33,7 +34,9 @@ func Applications(ctx *context.Context) {
 	ctx.Data["Title"] = ctx.Tr("settings.applications")
 	ctx.Data["PageIsAdminApplications"] = true
 
-	apps, err := auth.GetOAuth2ApplicationsByUserID(ctx, 0)
+	apps, err := db.Find[auth.OAuth2Application](ctx, auth.FindOAuth2ApplicationsOptions{
+		IsGlobal: true,
+	})
 	if err != nil {
 		ctx.ServerError("GetOAuth2ApplicationsByUserID", err)
 		return