feat: implement email notification for internship status updates and add missing student relationship

backend/app/Mail/InternshipStatusUpdated.php

@@ -0,0 +1,88 @@
+<?php
+
+namespace App\Mail;
+
+use App\Models\Internship;
+use Illuminate\Bus\Queueable;
+use Illuminate\Mail\Mailable;
+use Illuminate\Mail\Mailables\Content;
+use Illuminate\Mail\Mailables\Envelope;
+use Illuminate\Queue\SerializesModels;
+
+class InternshipStatusUpdated extends Mailable
+{
+    use Queueable, SerializesModels;
+
+    private Internship $internship;
+    private string $changedByName;
+    private string $studentName;
+    private string $companyName;
+    private string $oldStatus;
+    private string $newStatus;
+    private string $note;
+
+    /**
+     * Create a new message instance.
+     */
+    public function __construct(Internship $internship, string $changedByName, string $studentName, string $companyName, string $oldStatus, string $newStatus, string $note)
+    {
+        $this->internship = $internship;
+        $this->changedByName = $changedByName;
+        $this->studentName = $studentName;
+        $this->companyName = $companyName;
+        $this->oldStatus = $oldStatus;
+        $this->newStatus = $newStatus;
+        $this->note = $note;
+    }
+
+    /**
+     * Get the message envelope.
+     */
+    public function envelope(): Envelope
+    {
+        return new Envelope(
+            subject: 'Internship Status Updated',
+        );
+    }
+
+    /**
+     * Get the message content definition.
+     */
+    public function content(): Content
+    {
+        return new Content(
+            view: 'mail.internship.status_updated',
+            with: [
+                "internship" => $this->internship,
+                "changedByName" => $this->changedByName,
+                "studentName" => $this->studentName,
+                "companyName" => $this->companyName,
+                "oldStatus" => $this->prettyStatus($this->oldStatus),
+                "newStatus" => $this->prettyStatus($this->newStatus),
+                "note" => $this->note,
+            ]
+        );
+    }
+
+    /**
+     * Get the attachments for the message.
+     *
+     * @return array<int, \Illuminate\Mail\Mailables\Attachment>
+     */
+    public function attachments(): array
+    {
+        return [];
+    }
+
+    private function prettyStatus(string $status): string
+    {
+        return match ($status) {
+            'SUBMITTED' => 'Zadané',
+            'CONFIRMED' => 'Potvrdená',
+            'DENIED' => 'Zamietnutá',
+            'DEFENDED' => 'Obhájená',
+            'NOT_DEFENDED' => 'Neobhájená',
+            default => throw new \Exception("Invalid status: $status")
+        };
+    }
+}