Always use Permission objects instead of string

[dktapps]

Problem description

There are various places where strings have to be looked up as permissions before using them:

PocketMine-MP/src/permission/PermissibleInternal.php

Line 142 in 8cdc7d7

$perm = $permManager->getPermission($name);

PocketMine-MP/src/permission/PermissibleInternal.php

Line 191 in 8cdc7d7

$perm = $permManager->getPermission($name);

PocketMine-MP/src/plugin/PluginManager.php

Line 191 in 8cdc7d7

$opRoot = $permManager->getPermission(DefaultPermissions::ROOT_OPERATOR);

PocketMine-MP/src/command/Command.php

Line 106 in 8cdc7d7

if($permissionManager->getPermission($perm) === null){

This is problematic because it requires redundant checks for null when working with always-defined core permissions, and also allows passing in strings that can't be checked statically, allowing typos that only crash when the code is run.

Proposed solution

In all of these places, we should just use Permission objects directly. Using strings presents the possibility that the permission may not exist or may not have been registered. (To be fair, using Permission objects also doesn't guarantee registration. We should probably fix that too.)

Referencing permissions by their string IDs should only be done when loading stuff from configs, like in a permission management plugin. The IDs are intended for user use, not code use. Ergo, PermissionManager should only be interacted with to look up a permission by its ID.

DefaultPermissions should turn into a RegistryTrait user (or perhaps an enum with metadata) to remove the need for DefaultPermissionNames (which should never have been needed to begin with).

Alternative solutions that don't require API changes