revert(api): decouple api from curriculum

This reverts commit c077ffe4b9
via PR #40703

api-server/common/models/block.js

@@ -0,0 +1,9 @@
+import { Observable } from 'rx';
+
+export default function(Block) {
+  Block.on('dataSourceAttached', () => {
+    Block.findOne$ = Observable.fromNodeCallback(Block.findOne, Block);
+    Block.findById$ = Observable.fromNodeCallback(Block.findById, Block);
+    Block.find$ = Observable.fromNodeCallback(Block.find, Block);
+  });
+}