Allow Unicode characters in user slug

A user containing Unicode characters (e.g., "ñ") in the slug causes trouble both for browsing and cloning. For example, currently you are allowed to create a user with slug daureña but then some operations involving this user work, and some don't:

Web access

Works

• Accessing the user profile from browser history
• http://localhost:7990/users/dauren%CC%83a
• http://localhost:7990/admin/users/view?name=daure%C3%B1a

Doesn't work

• typing 'ñ'
• http://localhost:7990/users/daure%C3%B1a
• http://localhost:7990/admin/users/view?name=dauren%CC%83a

  Command-line

Works

• git clone http://dauren%CC%83a@localhost:7990/scm/~dauren%CC%83a/daurena.git
• git clone http://daure%C3%B1a@localhost:7990/scm/~dauren%CC%83a/daurena.git

Doesn't Work

• git clone http://daure%C3%B1a@localhost:7990/scm/~daure%C3%B1a/daurena.git
• git clone http://dauren%CC%83a@localhost:7990/scm/~daure%C3%B1a/daurena.git (Auth fails)
• git clone http://daureña@localhost:7990/scm/~daure%C3%B1a/daurena.git
• git clone http://daureña@localhost:7990/scm/~daureña/daurena.git

  Other symptoms of the problem

Renaming a user will return "The user could not be renamed":

Saving changes in the user details will return "The server didn't respond. You may retry your request when the server comes back up":

Changing the password will return "The password could not be changed":

When accessing the Global Permissions, the list of users and group will not load:

Workaround

Rename the user so that the slug contains only ASCII characters.

Alternative workaround

If the user cannot be renamed via the user interface:

1. Logout from Bitbucket Server

1. use the following query to update the SYS.ADMIN user
   Always back up your data before performing any modifications to the database. If possible, test any insert, update, or delete SQL commands on a staging server first.

   UPDATE sta_normal_user
   SET name = '<your_name>', slug = '<your_slug>'
   WHERE user_id = '<user_id>'