Update Events (#10)

This update restructures the events page code and provides additional functionality.
- Overwrite old entries on re-submission of previously used emails
- Build data and stats caches on launch for use in submission checks and stats regeneration
- Update to form content
- Move stats function to separate utils file

Reviewed-on: ayo/website#10
Co-authored-by: Jimmy Vargo <james@ayo.tokyo>
Co-committed-by: Jimmy Vargo <james@ayo.tokyo>

events/form_content.py

@@ -15,7 +15,20 @@ class FormContent:
         'topic-ai': 'AI / Deep Learning libraries ディープラーニングのライブラリー (Pytorch, Tensorflow, etc.) ',
         'topic-web-dev': 'Web Development ウェブ開発'
     }
+    background = {
+        'background-business': 'Business / Sales 営業',
+        'background-manager': 'Manager マネージャー',
+        'background-engineer': 'Engineer エンジニア',
+        'background-other': 'Other その他'
+    }
     languages = {
         'language-english': 'English 英語',
-        'language-japanese': 'Japanese 日本語',
+        'language-japanese': 'Japanese 日本語'
+    }
+
+    all_keys = set(times | topics | background | languages) | {
+        'name',
+        'email',
+        'topic-other',
+        'presentation-interest'
     }