[Multi-User Part 4]: Authenticate using API Tokens (#513)

### ✨ New
- Use API keys to authenticate from Desktop, Obsidian, Emacs clients
- Create API, UI on web app config page to CRUD API Keys
- Create user API keys table and functions to CRUD them in Database

### 🧪 Improve
- Default to better search model, [gte-small](https://huggingface.co/thenlper/gte-small), to improve search quality
- Only load chat model to GPU if enough space, throw error on load failure
- Show encoding progress, truncate headings to max chars supported
- Add instruction to create db in Django DB setup Readme

### ⚙️ Fix
- Fix error handling when configure offline chat via Web UI
- Do not warn in anon mode about Google OAuth env vars not being set
- Fix path to load static files when server started from project root

tests/helpers.py

@@ -3,6 +3,7 @@ import os
 
 from database.models import (
     KhojUser,
+    KhojApiUser,
     ConversationProcessorConfig,
     OfflineChatProcessorConversationConfig,
     OpenAIProcessorConversationConfig,
@@ -20,6 +21,15 @@ class UserFactory(factory.django.DjangoModelFactory):
     uuid = factory.Faker("uuid4")
 
 
+class ApiUserFactory(factory.django.DjangoModelFactory):
+    class Meta:
+        model = KhojApiUser
+
+    user = None
+    name = factory.Faker("name")
+    token = factory.Faker("password")
+
+
 class ConversationProcessorConfigFactory(factory.django.DjangoModelFactory):
     class Meta:
         model = ConversationProcessorConfig