refactor: Rename resourceExists to hasResource

The function was also moved to the smaller interface ResourceSet.

test/unit/http/ldp/PatchOperationHandler.test.ts

@@ -19,7 +19,7 @@ describe('A PatchOperationHandler', (): void => {
     operation = { method: 'PATCH', target: { path: 'http://test.com/foo' }, body, conditions, preferences: {}};
 
     store = {
-      resourceExists: jest.fn(),
+      hasResource: jest.fn(),
       modifyResource: jest.fn(),
     } as any;
 
@@ -47,7 +47,7 @@ describe('A PatchOperationHandler', (): void => {
   });
 
   it('returns the correct response if the resource already exists.', async(): Promise<void> => {
-    store.resourceExists.mockResolvedValueOnce(true);
+    store.hasResource.mockResolvedValueOnce(true);
     const result = await handler.handle({ operation });
     expect(store.modifyResource).toHaveBeenCalledTimes(1);
     expect(store.modifyResource).toHaveBeenLastCalledWith(operation.target, body, conditions);