Refactored the T-SQL scripting for user-role assignments to enforce independence between scripts.
This change removes the need to track which roles have been scripted, preventing dependency issues when scripts are
run out of order. Below is a detailed introduction to the issue and the solution.

In this new approach of scripting, we do not maintain a variable to track the roles that have been scripted. Our
method involves a consistent verification process for each user against the complete list of roles. This ensures that
we dynamically include only the roles to which a user belongs. For example, consider two users: user1 is associated
with role1 and role2, while user2 is associated with role1 and role3.

Attempting to memorize the scripted roles could result in Transact-SQL (T-SQL) statements such as:

```
IF NOT EXISTS (role1)
  CREATE ROLE role1
IF NOT EXISTS (role2)
  CREATE ROLE role2
IF NOT EXISTS (user1)
  CREATE USER user1
ADD user1 TO role1
ADD user1 TO role2

-- And for another user:

IF NOT EXISTS (role3)
  CREATE ROLE role3
IF NOT EXISTS (user2)
  CREATE USER user2
ADD user2 TO role1
ADD user2 TO role3
```
`

However, this script inadvertently introduces a dependency issue. To ensure user2 is properly configured, the script
segment for user1 must be executed first due to the shared role1. To circumvent this issue and remove interdependencies,
we opt to match each user against all potential roles. Consequently, roles are scripted per user membership, resulting
in T-SQL like:

```
IF NOT EXISTS (role1)
  CREATE ROLE role1
IF NOT EXISTS (role2)
  CREATE ROLE role2
IF NOT EXISTS (user1)
  CREATE USER user1
ADD user1 TO role1
ADD user1 TO role2

-- And for another user:

IF NOT EXISTS (role1)
  CREATE ROLE role1
IF NOT EXISTS (role3)
  CREATE ROLE role3
IF NOT EXISTS (user2)
  CREATE USER user2
ADD user2 TO role1
ADD user2 TO role3
```

While this method may produce some redundant code (e.g., checking and creating role1 twice), it guarantees that each
portion of the script is self-sufficient and can be executed independently of others. Therefore, users can selectively
execute any segment of the script without concern for execution order or dependencies.