Refactor data handlers + misc fixes

This refactors the data handlers into a more standard/understood model-like architecture, to prepare for a new, more robust config system.

It also fixes a problem with creating new Notes and uploading new Photos via the web interface (related to #58).

Finally, it speeds up docker builds by sending in less files, which aren't necessary or will be built anyway.

This is all in preparation to allow building #13 more robustly.

lib/config.ts

@@ -1,11 +1,11 @@
 import 'std/dotenv/load.ts';
 
-import { isThereAnAdmin } from './data/user.ts';
+import { UserModel } from './models/user.ts';
 
 export async function isSignupAllowed() {
   const areSignupsAllowed = Deno.env.get('CONFIG_ALLOW_SIGNUPS') === 'true';
 
-  const areThereAdmins = await isThereAnAdmin();
+  const areThereAdmins = await UserModel.isThereAnAdmin();
 
   if (areSignupsAllowed || !areThereAdmins) {
     return true;