chore: update document approval workflow and bug fixes

Modules/ApprovalWorkflow/app/Models/ApprovalChain.php

@@ -0,0 +1,76 @@
+<?php
+
+namespace Modules\ApprovalWorkflow\Models;
+
+use App\Models\User;
+use App\Traits\HasPublicIdentifier;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\MorphTo;
+use Modules\ApprovalWorkflow\Enums\ApprovalChainStatus;
+
+class ApprovalChain extends Model
+{
+    use HasPublicIdentifier;
+
+    protected $fillable = [
+        'approvable_type',
+        'approvable_id',
+        'type',
+        'status',
+        'notes',
+        'initiated_by',
+        'completed_at',
+    ];
+
+    protected function casts(): array
+    {
+        return [
+            'status' => ApprovalChainStatus::class,
+            'completed_at' => 'datetime',
+        ];
+    }
+
+    public function approvable(): MorphTo
+    {
+        return $this->morphTo();
+    }
+
+    public function initiator(): BelongsTo
+    {
+        return $this->belongsTo(User::class, 'initiated_by');
+    }
+
+    public function steps(): HasMany
+    {
+        return $this->hasMany(ApprovalStep::class)->orderBy('order');
+    }
+
+    public function currentStep(): ?ApprovalStep
+    {
+        return $this->steps()->where('status', 'pending')->first();
+    }
+
+    public function isFullyApproved(): bool
+    {
+        return $this->steps()->where('status', '!=', 'approved')->doesntExist();
+    }
+
+    public function transitionTo(ApprovalChainStatus $newStatus): void
+    {
+        $allowed = $this->status->allowedTransitions();
+        if (!in_array($newStatus, $allowed)) {
+            throw new \InvalidArgumentException(
+                "Cannot transition chain from {$this->status->label()} to {$newStatus->label()}"
+            );
+        }
+
+        $updates = ['status' => $newStatus];
+        if (in_array($newStatus, [ApprovalChainStatus::Approved, ApprovalChainStatus::Rejected])) {
+            $updates['completed_at'] = now();
+        }
+
+        $this->update($updates);
+    }
+}