feat: add additional supported interfaces

This includes the relevant auth headers and a simplification of several others.

src/authorization/Authorizer.ts

@@ -0,0 +1,23 @@
+import { Credentials } from '../authentication/Credentials';
+import { PermissionSet } from '../ldp/permissions/PermissionSet';
+import { ResourceIdentifier } from '../ldp/http/ResourceIdentifier';
+
+/**
+ * Responsible for the permission verification.
+ */
+export interface Authorizer {
+  /**
+   * Verifies if the given credentials have access to the given permissions on the given resource.
+   * @param credentials - Credentials of the entity that wants to use the resource.
+   * @param identifier - Identifier of the resource that will be read/modified.
+   * @param permissions - Permissions that are requested on the resource.
+   *
+   * @returns A promise resolving when the Authorizer is finished.
+   * An {@link Error} with the necessary explanation will be thrown when permissions are not granted.
+   */
+  ensurePermissions: (
+    credentials: Credentials,
+    identifier: ResourceIdentifier,
+    permissions: PermissionSet,
+  ) => Promise<void>;
+}