An attempt to wrap the API with JWT

Lots of hardcoded stuff and assumptions, but works as expected. It can
be run as a service with a config like this
```
c.JupyterHub.load_roles = [
    {
        "name": "jwt",
        "scopes": [
            "read:users:activity",  # read user last_activity
            "servers",  # start and stop servers
            "admin:users",  # needed if culling idle users as well
        ],
    },
    {
        "name": "user",
        "scopes": ["access:services", "self"],
    },
]

c.JupyterHub.services = [
    {
        "name": "jwt",
        "url": "http://localhost:1984/",
        # any secret >8 characters, you'll use api_token to
        # authenticate api requests to the hub from your service
        "api_token": "super-secret",
    }
]
```

and then start the service:
```
fastapi dev --port 1984 api_wrapper.py
```

egi_notebooks_hub/services/api_wrapper.py

@@ -0,0 +1,43 @@
+from typing import Union
+
+from fastapi import FastAPI, Request
+import httpx
+
+app = FastAPI()
+
+AUTH_HEADER = "Authorization"
+TOKEN_TYPE = "bearer"
+URL = "http://localhost:8000/hub/jwt_login"
+API_URL = "http://localhost:8000/hub/api"
+PREFIX = "services/jwt"
+
+
+async def request(client):
+    response = await client.get(URL)
+    return response.text
+
+
+# this could be way more generic and moved to a base function and then
+# a thin wrapper for get/put/post/etc...
+@app.get("/{svc_path:path}")
+async def api_wrapper(request: Request, svc_path: str):
+    user_token = {}
+    if AUTH_HEADER in request.headers:
+        f = request.headers[AUTH_HEADER].split()
+        if len(f) == 2 and f[0].lower() == TOKEN_TYPE:
+            async with httpx.AsyncClient() as client:
+                r = await client.get(
+                    URL, headers={AUTH_HEADER: request.headers[AUTH_HEADER]}
+                )
+                # errors should kick me out
+                user_token = r.json()
+    # assume we have the user_token here
+    api_path = svc_path.removeprefix(PREFIX)
+    print(svc_path)
+    print(api_path)
+    async with httpx.AsyncClient() as client:
+        # which headers do we need to preserve?
+        headers = {"Authorization": f"token {user_token['token']}"}
+        r = await client.get(API_URL + api_path, headers=headers)
+        # is this a correct assumption?
+        return r.json()