Add kontonummer fallback to HIUPDv6 if IBAN is not available

.gitignore

@@ -1,5 +1,6 @@
 .DS_Store
 .idea/
+.vscode/
 vendor/
 develop/
 coverage/

lib/Fhp/Segment/HIUPD/HIUPDv6.php

@@ -53,7 +53,11 @@ class HIUPDv6 extends BaseSegment implements HIUPD
 
     public function matchesAccount(SEPAAccount $account): bool
     {
-        return !is_null($this->iban) && $this->iban == $account->getIban();
+        if (!is_null($this->iban)) {
+            return $this->iban == $account->getIban();
+        }
+        // Sparkasse (Koblenz) does not provide an IBAN in this segment, fall back to kontonummer:
+        return !is_null($this->kontoverbindung->kontonummer) && $this->kontoverbindung->kontonummer == $account->getAccountNumber();
     }
 
     public function getErlaubteGeschaeftsvorfaelle(): array

lib/Fhp/Syntax/Serializer.php

@@ -77,7 +77,7 @@ public static function serializeSegment(BaseSegment $segment): string
      */
     public static function serializeSegments(array $segments): string
     {
-        return implode(array_map(['self', 'serializeSegment'], $segments));
+        return implode(array_map([self::class, 'serializeSegment'], $segments));
     }
 
     /**