docs: Add info for the password hashes

Signed-off-by: Christopher Ng <chrng8@gmail.com>

lib/public/IUser.php

@@ -79,6 +79,7 @@ interface IUser {
 	/**
 	 * Get the password hash of the user
 	 *
+	 * @return ?string the password hash hashed by `\OCP\Security\IHasher::hash()`
 	 * @since 30.0.0
 	 */
 	public function getPasswordHash(): ?string;
@@ -86,6 +87,8 @@ interface IUser {
 	/**
 	 * Set the password hash of the user
 	 *
+	 * @param string $passwordHash the password hash hashed by `\OCP\Security\IHasher::hash()`
+	 * @throws InvalidArgumentException when `$passwordHash` is not a valid hash
 	 * @since 30.0.0
 	 */
 	public function setPasswordHash(string $passwordHash): bool;

lib/public/User/Backend/IPasswordHashBackend.php

@@ -9,16 +9,21 @@ declare(strict_types=1);
 
 namespace OCP\User\Backend;
 
+use InvalidArgumentException;
+
 /**
  * @since 30.0.0
  */
 interface IPasswordHashBackend {
 	/**
+	 * @return ?string the password hash hashed by `\OCP\Security\IHasher::hash()`
 	 * @since 30.0.0
 	 */
 	public function getPasswordHash(string $userId): ?string;
 
 	/**
+	 * @param string $passwordHash the password hash hashed by `\OCP\Security\IHasher::hash()`
+	 * @throws InvalidArgumentException when `$passwordHash` is not a valid hash
 	 * @since 30.0.0
 	 */
 	public function setPasswordHash(string $userId, string $passwordHash): bool;