Return null event_source_url when scheme is missing

Summary:
Update `constructEventSourceUrl()` to return null when `$data->scheme` is empty, instead of defaulting to `"http"`. If scheme is null/empty, it means the adaptor was not called or no scheme data is available — defaulting to `"http"` would produce a potentially incorrect URL.

The adaptor (`RequestContextAdaptor::extract()`) already guarantees a non-null scheme (`"http"` or `"https"`) when server context is available. The fallback to `"http"` belongs in the adaptor, not in the URL construction logic.

Changes:
- `constructEventSourceUrl()`: Add `empty($data->scheme)` to the null guard
- `constructEventSourceUrl()`: Use `$data->scheme` directly instead of `$data->scheme ?? "http"`
- `EventSourceUrlTest.php`: Update tests that previously expected `"http://..."` when scheme was null to expect null instead

Reviewed By: jyou23github

Differential Revision: D105385176

fbshipit-source-id: 69c28d7c1a3d0dde08c54796d70480881cc97bc9

Author: haretonj

php/capi-param-builder/src/ParamBuilder.php

@@ -357,12 +357,12 @@ public function getEventSourceUrl()
 
     private function constructEventSourceUrl($data)
     {
-        if ($data === null || empty($data->host)) {
+        if ($data === null || empty($data->host) || empty($data->scheme)) {
             $this->event_source_url = null;
             return;
         }
 
-        $url = ($data->scheme ?? 'http') . '://';
+        $url = $data->scheme . '://';
         $url .= $data->host;
 
         if (!empty($data->request_uri)) {

php/capi-param-builder/tests/EventSourceUrlTest.php

@@ -294,7 +294,7 @@ public function testEventSourceUrlHttpWithHostAndUri(): void
         $this->assertEquals('http://www.example.com/path', $builder->getEventSourceUrl());
     }
 
-    public function testEventSourceUrlHttpWhenSchemeNull(): void
+    public function testEventSourceUrlNullWhenSchemeNull(): void
     {
         $builder = new ParamBuilder();
         $data = new PlainDataObject(
@@ -308,7 +308,7 @@ public function testEventSourceUrlHttpWhenSchemeNull(): void
             '/path'
         );
         $builder->processRequestFromContext($data);
-        $this->assertEquals('http://www.example.com/path', $builder->getEventSourceUrl());
+        $this->assertNull($builder->getEventSourceUrl());
     }
 
     public function testEventSourceUrlNullWhenAllNull(): void
@@ -328,7 +328,7 @@ public function testEventSourceUrlNullWhenAllNull(): void
         $this->assertNull($builder->getEventSourceUrl());
     }
 
-    public function testEventSourceUrlHostOnly(): void
+    public function testEventSourceUrlNullWhenHostOnlyNoScheme(): void
     {
         $builder = new ParamBuilder();
         $data = new PlainDataObject(
@@ -342,7 +342,7 @@ public function testEventSourceUrlHostOnly(): void
             null
         );
         $builder->processRequestFromContext($data);
-        $this->assertEquals('http://host.example.com', $builder->getEventSourceUrl());
+        $this->assertNull($builder->getEventSourceUrl());
     }
 
     public function testEventSourceUrlPreservesQueryString(): void