Add phpstan level 7(#544)

app/Traits/Enum.php

@@ -4,6 +4,9 @@
 
 trait Enum
 {
+    /**
+     * @return array<string, mixed>
+     */
     public static function all(): array
     {
         $reflection = new \ReflectionClass(self::class);

app/Traits/HasProjectThroughServer.php

@@ -8,6 +8,9 @@
 
 trait HasProjectThroughServer
 {
+    /**
+     * @return HasOneThrough<Project, Server, $this>
+     */
     public function project(): HasOneThrough
     {
         return $this->hasOneThrough(

app/Traits/HasTimezoneTimestamps.php

@@ -21,7 +21,7 @@ public function getUpdatedAtByTimezoneAttribute(): string
         return $this->getDateTimeByTimezone($this->updated_at);
     }
 
-    public function getDateTimeByTimezone(?Carbon $value = null): ?string
+    public function getDateTimeByTimezone(?Carbon $value = null): string
     {
         if ($value && auth()->user() && auth()->user()->timezone) {
             try {
@@ -30,6 +30,6 @@ public function getDateTimeByTimezone(?Carbon $value = null): ?string
             }
         }
 
-        return $value;
+        return $value ?? '';
     }
 }