fix: correct environment variable handling in MSSQL tests

Fixed issue where MSSQL tests were failing in GitHub Actions with
'Login failed for user testuser' error. The problem was incorrect
handling of getenv() return values.

Changes:
1. Fixed BaseMSSQLTestCase::setUpBeforeClass():
   - Changed from: getenv('PDODB_USERNAME') ?: self::DB_USER
   - Changed to: explicit check for false or empty string
   - getenv() returns false for non-existent variables, and ?: operator
     doesn't work correctly with false values

2. Fixed OptimizeCommandCliTests::setUp():
   - Changed from: getenv('PDODB_USERNAME') ?: self::DB_USER
   - Changed to: explicit check for false or empty string
   - Ensures environment variables from GitHub Actions (sa/Test123!@#)
     are properly read instead of falling back to testuser/testpass

The issue affected 18 tests that were trying to connect with
'testuser' credentials instead of 'sa' credentials provided by
GitHub Actions environment variables.

Search keywords for future debugging:
- MSSQL test login failed
- environment variable getenv false
- GitHub Actions MSSQL credentials
- PDODB_USERNAME PDODB_PASSWORD handling

Author: tommyknocker

tests/mssql/BaseMSSQLTestCase.php

@@ -31,8 +31,14 @@ public static function setUpBeforeClass(): void
          * PDODB_USERNAME=sa PDODB_PASSWORD=Test123!@#
          */
         // Use environment variables if set (for CI), otherwise use constants
-        $username = getenv('PDODB_USERNAME') ?: self::DB_USER;
-        $password = getenv('PDODB_PASSWORD') ?: self::DB_PASSWORD;
+        $username = getenv('PDODB_USERNAME');
+        if ($username === false || $username === '') {
+            $username = self::DB_USER;
+        }
+        $password = getenv('PDODB_PASSWORD');
+        if ($password === false || $password === '') {
+            $password = self::DB_PASSWORD;
+        }
 
         self::$db = new PdoDb(
             'sqlsrv',

tests/mssql/OptimizeCommandCliTests.php

@@ -17,8 +17,15 @@ public function setUp(): void
     {
         parent::setUp();
         // Set environment variables for Application
-        $username = getenv('PDODB_USERNAME') ?: self::DB_USER;
-        $password = getenv('PDODB_PASSWORD') ?: self::DB_PASSWORD;
+        // Read from environment first (for CI), then fallback to constants
+        $username = getenv('PDODB_USERNAME');
+        if ($username === false || $username === '') {
+            $username = self::DB_USER;
+        }
+        $password = getenv('PDODB_PASSWORD');
+        if ($password === false || $password === '') {
+            $password = self::DB_PASSWORD;
+        }
         putenv('PDODB_DRIVER=sqlsrv');
         putenv('PDODB_HOST=' . self::DB_HOST);
         putenv('PDODB_PORT=' . (string)self::DB_PORT);