Implement Keystone environment deployments

app/Models/EnvironmentAttachment.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace App\Models;
+
+use App\Enums\EnvironmentAttachmentRole;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class EnvironmentAttachment extends Model
+{
+    protected $guarded = [];
+
+    protected function casts(): array
+    {
+        return [
+            'is_primary' => 'boolean',
+            'role' => EnvironmentAttachmentRole::class,
+        ];
+    }
+
+    public function environment(): BelongsTo
+    {
+        return $this->belongsTo(Environment::class);
+    }
+
+    public function service(): BelongsTo
+    {
+        return $this->belongsTo(Service::class);
+    }
+
+    public function serviceSlice(): BelongsTo
+    {
+        return $this->belongsTo(ServiceSlice::class);
+    }
+}