Add filter function to QueryBuilder

Signed-off-by: davidarendsen <davidarendsen@hey.com>

tests/QueryBuilderTest.php

@@ -1,6 +1,7 @@
 <?php
 declare(strict_types=1);
 
+use Arendsen\FluxQueryBuilder\Expression\KeyValue;
 use PHPUnit\Framework\TestCase;
 use Arendsen\FluxQueryBuilder\QueryBuilder;
 
@@ -9,27 +10,43 @@ final class QueryBuilderTest extends TestCase {
     /**
      * @dataProvider simpleQueryProvider
      */
-    public function testSimpleQuery($bucket, $measurement, $range, $expectedQuery)
+    public function testSimpleQuery($bucket, $measurement, $range, $keyValue, $expectedQuery)
     {
         $queryBuilder = new QueryBuilder();
         $queryBuilder->from($bucket)
             ->fromMeasurement($measurement)
 			->addRangeStart($range);
 
+        if($keyValue)
+        {
+            $queryBuilder->addFilter($keyValue);
+        }
+
         $this->assertEquals($expectedQuery, $queryBuilder->build());
     }
 
     public function simpleQueryProvider(): array
     {
         return [
-            'case 1' => [
+            'basic query' => [
                 [
                     'bucket' => 'example_bucket',
                 ],
                 'test_measurement',
                 '-360h',
+                null,
                 'from(bucket: "example_bucket") |> range(start: "-360h") |> filter(fn: (r) => r._measurement == "test_measurement") '
             ],
+            'query with filter' => [
+                [
+                    'bucket' => 'example_bucket',
+                ],
+                'test_measurement',
+                '-360h',
+                new KeyValue('user', 'username'),
+                'from(bucket: "example_bucket") |> range(start: "-360h") |> filter(fn: (r) => r._measurement == "test_measurement") ' . 
+                    '|> filter(fn: (r) => r.user == "username") '
+            ],
         ];
     }