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

## :warning: BREAKING :warning:

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

2 files changed, 10 insertions, 4 deletions

diff --git a/docs/content/installation/database-preparation.en-us.md b/docs/content/installation/database-preparation.en-us.md
index 5e0b94665f..e6abb8a613 100644
--- a/docs/content/installation/database-preparation.en-us.md
+++ b/docs/content/installation/database-preparation.en-us.md
@@ -61,10 +61,14 @@ Note: All steps below requires that the database engine of your choice is instal
 
     Replace username and password above as appropriate.
 
-4. Create database with UTF-8 charset and collation. Make sure to use `utf8mb4` charset instead of `utf8` as the former supports all Unicode characters (including emojis) beyond _Basic Multilingual Plane_. Also, collation chosen depending on your expected content. When in doubt, use either `unicode_ci` or `general_ci`.
+4. Create database with UTF-8 charset and case-sensitive collation.
+
+    `utf8mb4_bin` is a common collation for both MySQL/MariaDB.
+    When Gitea starts, it will try to find a better collation (`utf8mb4_0900_as_cs` or `uca1400_as_cs`) and alter the database if it is possible.
+    If you would like to use other collation, you can set `[database].CHARSET_COLLATION` in the `app.ini` file.
 
     ```sql
-    CREATE DATABASE giteadb CHARACTER SET 'utf8mb4' COLLATE 'utf8mb4_unicode_ci';
+    CREATE DATABASE giteadb CHARACTER SET 'utf8mb4' COLLATE 'utf8mb4_bin';
     ```
 
     Replace database name as appropriate.
diff --git a/docs/content/installation/database-preparation.zh-cn.md b/docs/content/installation/database-preparation.zh-cn.md
index b58344133e..d651088395 100644
--- a/docs/content/installation/database-preparation.zh-cn.md
+++ b/docs/content/installation/database-preparation.zh-cn.md
@@ -59,10 +59,12 @@ menu:
 
     根据需要替换上述用户名和密码。
 
-4. 使用 UTF-8 字符集和排序规则创建数据库。确保使用 `**utf8mb4**` 字符集，而不是 `utf8`，因为前者支持 _Basic Multilingual Plane_ 之外的所有 Unicode 字符（包括表情符号）。排序规则根据您预期的内容选择。如果不确定，可以使用 `unicode_ci` 或 `general_ci`。
+4. 使用 UTF-8 字符集和大小写敏感的排序规则创建数据库。
+
+    Gitea 启动后会尝试把数据库修改为更合适的字符集，如果你想指定自己的字符集规则，可以在 app.ini 中设置 `[database].CHARSET_COLLATION`。
 
     ```sql
-    CREATE DATABASE giteadb CHARACTER SET 'utf8mb4' COLLATE 'utf8mb4_unicode_ci';
+    CREATE DATABASE giteadb CHARACTER SET 'utf8mb4' COLLATE 'utf8mb4_bin';
     ```
 
     根据需要替换数据库名称。