Document MSSQL database preparation (#636)

The database preparation page covered only MySQL and PostgreSQL. MSSQL setups without schema permissions break on upgrades, like in https://github.com/go-gitea/gitea/issues/40256.

The new section shows the login, database and user setup with the roles Gitea needs, for main and 28, including zh-cn and zh-tw.

_Written by Claude (Opus 5.5)._

Reviewed-on: https://gitea.com/gitea/docs/pulls/636
Reviewed-by: Lunny Xiao <[email protected]>
Co-authored-by: silverwind <[email protected]>

versioned_docs/version-28/installation/database-preparation.md

@@ -8,7 +8,7 @@ aliases:
 
 # Database Preparation
 
-You need a database to use Gitea. Gitea supports PostgreSQL (>= 12), MySQL (>= 8.0), MariaDB (>= 10.4), SQLite (builtin), and MSSQL (>= 2012 SP4). This page will guide into preparing database. Only PostgreSQL and MySQL will be covered here since those database engines are widely-used in production. If you plan to use SQLite, you can ignore this chapter.
+You need a database to use Gitea. Gitea supports PostgreSQL (>= 12), MySQL (>= 8.0), MariaDB (>= 10.4), SQLite (builtin), and MSSQL (>= 2012 SP4). This page will guide into preparing database. PostgreSQL, MySQL and MSSQL are covered here. If you plan to use SQLite, you can ignore this chapter.
 
 :::warning
 Converting one database type to another is not a well-tested process and you may experience issues. It is better to choose the final database type at the type of the first installation. Be aware that SQLite does not scale; if you expect your instance to grow at a later time, you should choose another database type.
@@ -177,6 +177,28 @@ All steps below requires that the database engine of your choice is installed on
 
     You should be prompted to enter password for the database user, and connected to the database.
 
+## MSSQL
+
+1. As an administrator, create the login, a database with case-sensitive collation, and its user. Replace the password `'gitea'` with a secure one:
+
+    ```sql
+    CREATE LOGIN gitea WITH PASSWORD = 'gitea';
+    CREATE DATABASE giteadb COLLATE Latin1_General_CS_AS;
+    GO
+    USE giteadb;
+    CREATE USER gitea FOR LOGIN gitea;
+    ALTER ROLE db_owner ADD MEMBER gitea;
+    GO
+    ```
+
+    Upgrades change the database schema, so the user needs `db_owner`, or `db_ddladmin`, `db_datareader` and `db_datawriter`. With the latter, also run `ALTER DATABASE giteadb SET READ_COMMITTED_SNAPSHOT ON;` as administrator.
+
+2. On your Gitea server, test the connection to the database:
+
+    ```sh
+    sqlcmd -S 203.0.113.3 -U gitea -d giteadb
+    ```
+
 ## Database Connection over TLS
 
 If the communication between Gitea and your database instance is performed through a private network, or if Gitea and the database are running on the same server, this section can be omitted since the security between Gitea and the database instance is not critically exposed. If instead the database instance is on a public network, use TLS to encrypt the connection to the database, as it is possible for third-parties to intercept the traffic data.