Add return types to tests and final|internal|private methods

Author: nicolas-grekas

Header/DateHeader.php

@@ -35,10 +35,7 @@ public function setBody($body)
         $this->setDateTime($body);
     }
 
-    /**
-     * @return \DateTimeImmutable
-     */
-    public function getBody()
+    public function getBody(): \DateTimeImmutable
     {
         return $this->getDateTime();
     }

Header/IdentificationHeader.php

@@ -44,10 +44,7 @@ public function setBody($body)
         $this->setId($body);
     }
 
-    /**
-     * @return array
-     */
-    public function getBody()
+    public function getBody(): array
     {
         return $this->getIds();
     }

Header/MailboxHeader.php

@@ -42,10 +42,8 @@ public function setBody($body)
 
     /**
      * @throws RfcComplianceException
-     *
-     * @return Address
      */
-    public function getBody()
+    public function getBody(): Address
     {
         return $this->getAddress();
     }

Header/MailboxListHeader.php

@@ -48,7 +48,7 @@ public function setBody($body)
      *
      * @return Address[]
      */
-    public function getBody()
+    public function getBody(): array
     {
         return $this->getAddresses();
     }

Header/PathHeader.php

@@ -40,10 +40,7 @@ public function setBody($body)
         $this->setAddress($body);
     }
 
-    /**
-     * @return Address
-     */
-    public function getBody()
+    public function getBody(): Address
     {
         return $this->getAddress();
     }