fix: make check_user_exists() work with FastAPI

docs/guide/fastapi_transition.md

@@ -1,3 +1,21 @@
+## Check if a user exists and access user object
+**old:**
+```python
+# decorators
+@check_user_exists()
+async def do_routing_stuff():
+    pass
+```
+
+**new:**
+If user doesn't exist, `Depends(check_user_exists)` will raise an exception.
+If user exists, `user` will be the user object
+```python
+# depends calls
+@core_html_routes.get("/my_route")
+async def extensions(user: User = Depends(check_user_exists)):
+    pass
+```
 ## Returning data from API calls
 **old:**
 ```python
@@ -48,6 +66,39 @@ raise HTTPException(
     detail=f"Failed to connect to {domain}."
 )
 ```
+
+## Extensions
+**old:**
+```python
+from quart import Blueprint
+
+amilk_ext: Blueprint = Blueprint(
+    "amilk", __name__, static_folder="static", template_folder="templates"
+)
+```
+
+**new:**
+```python
+from fastapi import APIRouter
+from lnbits.jinja2_templating import Jinja2Templates
+from lnbits.helpers import template_renderer
+from fastapi.staticfiles import StaticFiles
+
+offlineshop_ext: APIRouter = APIRouter(
+    prefix="/Extension",
+    tags=["Offlineshop"]
+)
+
+offlineshop_ext.mount(
+    "lnbits/extensions/offlineshop/static",
+    StaticFiles("lnbits/extensions/offlineshop/static")
+)
+
+offlineshop_rndr = template_renderer([
+    "lnbits/extensions/offlineshop/templates",
+])
+```
+
 ## Possible optimizations
 ### Use Redis as a cache server
 Instead of hitting the database over and over again, we can store a short lived object in [Redis](https://redis.io) for an arbitrary key.

lnbits/decorators.py

@@ -2,7 +2,8 @@ from functools import wraps
 from http import HTTPStatus
 
 from fastapi.security import api_key
-from lnbits.core.models import Wallet
+from pydantic.types import UUID4
+from lnbits.core.models import User, Wallet
 from typing import List, Union
 from uuid import UUID
 
@@ -138,29 +139,18 @@ def api_validate_post_request(*, schema: dict):
     return wrap
 
 
-def check_user_exists(param: str = "usr"):
-    def wrap(view):
-        @wraps(view)
-        async def wrapped_view(**kwargs):
-            g().user = await get_user(request.args.get(param, type=str)) 
-            if not g().user:
-                raise HTTPException(
-                    status_code=HTTPStatus.NOT_FOUND,
-                    detail="User  does not exist."
-                )
-
-            if LNBITS_ALLOWED_USERS and g().user.id not in LNBITS_ALLOWED_USERS:
-                raise HTTPException(
-                    status_code=HTTPStatus.UNAUTHORIZED,
-                    detail="User not authorized."
-                )
-                
-
-            return await view(**kwargs)
-
-        return wrapped_view
-
-    return wrap
-
+async def check_user_exists(usr: UUID4) -> User:
+    g().user = await get_user(usr.hex) 
+    if not g().user:
+        raise HTTPException(
+            status_code=HTTPStatus.NOT_FOUND,
+            detail="User  does not exist."
+        )
 
+    if LNBITS_ALLOWED_USERS and g().user.id not in LNBITS_ALLOWED_USERS:
+        raise HTTPException(
+            status_code=HTTPStatus.UNAUTHORIZED,
+            detail="User not authorized."
+        )
 
+    return g().user