Return a dummy download hash for Godot editor API compatibility

app/Asset.php

@@ -188,6 +188,7 @@ class Asset extends Model
     protected $appends = [
         'category',
         'tags',
+        'download_hash',
         'download_url',
         'godot_version',
         'icon_url',
@@ -392,6 +393,18 @@ public function setBrowseUrlAttribute(string $browseUrl): void
         }
     }
 
+    /**
+     * Placeholder to make the Godot editor accept the download hash but not verify it.
+     *
+     * TODO: Consider computing the download hash on a per-version basis and store it.
+     *       However, this may not be a good idea as GitHub ZIP hashes aren't guaranteed
+     *       to be the same over a long period of time.
+     */
+    public function getDownloadHashAttribute(): string
+    {
+        return '';
+    }
+
     /**
      * Return the download URL corresponding to the latest version
      * (for compatibility with the existing API).

public/developer/v1/openapi.yaml

@@ -111,16 +111,22 @@ components:
           format: url
           description: >
             The asset's changelog URL.
-        donate_url:
+        download_hash:
           type: string
-          format: url
+          default: ''
           description: >
-            The asset's donation URL. This can be set by the author to receive donations (using services like Patreon or GitHub Sponsors).
+            The asset's SHA-256 hash for the latest version.
+            **Note:** This is currently always an empty string as asset versions' hashes aren't computed and stored yet.
         cost:
           type: string
           description: >
             The asset's license as a [SPDX license identifier](https://spdx.org/licenses/).
             For compatibility reasons, this field is called `cost` instead of `license`.
+        donate_url:
+          type: string
+          format: url
+          description: >
+            The asset's donation URL. This can be set by the author to receive donations (using services like Patreon or GitHub Sponsors).
         godot_version:
           type: string
           description: >