feat: implement local cookie authentication

This is only useful for application running directly on the Raspiblitz.
This will create a file in ~/.blitz_api/.cookie with a valid JWT token.
Local applications can use this to authenticate to the API without
having to ask for the password. This is similar to how Bitcoin Cores
cookie auth works.

.env_sample

@@ -6,6 +6,11 @@ jwt_expiry_time=300
 # login password
 login_password=12345678
 
+# Enable this if you want to run blitz_gui locally.
+# This will create a file called ~/blitz_api/.cookie with a
+# JWT token.
+# enable_local_cookie_auth = false
+
 # Amount of seconds the app will wait until it'll 
 # send another hardware update
 gather_hw_info_interval = 2

app/auth/auth_handler.py

@@ -1,3 +1,5 @@
+import asyncio
+import os
 import time
 from typing import Dict
 
@@ -29,3 +31,39 @@ def decodeJWT(token: str) -> dict:
     except Exception as e:
         print(f"Unable to decode jwt_token {e}")
         return {}
+
+
+def handle_local_cookie():
+    remove_local_cookie()
+
+    blitz_path = os.path.join(os.path.expanduser("~"), ".blitz_api")
+    full_cookie_file_path = os.path.join(blitz_path, ".cookie")
+    enabled = config("enable_local_cookie_auth", default=False, cast=bool)
+
+    if not os.path.exists(blitz_path):
+        os.makedirs(blitz_path)
+
+    if enabled:
+        f = open(full_cookie_file_path, "w")
+        f.write(signJWT()["access_token"])
+        f.close()
+
+
+def remove_local_cookie():
+    full_cookie_file_path = os.path.join(
+        os.path.expanduser("~"), ".blitz_api", ".cookie"
+    )
+
+    if os.path.exists(path=full_cookie_file_path):
+        os.remove(full_cookie_file_path)
+
+
+def register_cookie_updater():
+    # We need to update the cookie file once the cookie is expired
+    async def _cookie_updater():
+        while True:
+            await asyncio.sleep(JWT_EXPIRY_TIME - 10)
+            handle_local_cookie()
+
+    loop = asyncio.get_event_loop()
+    loop.create_task(_cookie_updater())

app/main.py

@@ -15,6 +15,11 @@ from starlette import status
 from starlette.middleware.cors import CORSMiddleware
 from starlette.responses import RedirectResponse
 
+from app.auth.auth_handler import (
+    handle_local_cookie,
+    register_cookie_updater,
+    remove_local_cookie,
+)
 from app.external.fastapi_versioning import VersionedFastAPI
 from app.external.sse_startlette import EventSourceResponse
 from app.repositories.bitcoin import (
@@ -73,11 +78,14 @@ async def on_startup():
     await redis_plugin.init_app(app, config=config)
     await redis_plugin.init()
     await register_all_handlers(redis_plugin.redis)
+    handle_local_cookie()
+    register_cookie_updater()
 
 
 @app.on_event("shutdown")
 async def on_shutdown() -> None:
     await redis_plugin.terminate()
+    remove_local_cookie()
 
 
 @app.get("/")