Update auth lib

Closing https://gitlab.cern.ch/webservices/authz-api-client/-/issues/1

Changed the library used for interaction with Authz API, instead of PyJWT we use Authlib, which provides more complete set of functions and is easier to use (less code).

This library is also used in the webservices-portal project.

Also moved the 'TARGET_API' into the api_token.py, as this doesn't need to be exposed higher up (all calls are made to the Authorization API).

authz_api_client/api_token.py

 import argparse
-from pprint import pprint
-import jwt
-import requests
+from authlib.integrations.requests_client import OAuth2Session
 import logging
-import datetime
 
 DEFAULT_SERVER = "auth.cern.ch"
 DEFAULT_REALM = "cern"
 DEFAULT_REALM_PREFIX = "auth/realms/{}"
 DEFAULT_TOKEN_ENDPOINT = "api-access/token"
+TARGET_API = "authorization-service-api"
 
 
 def get_token_endpoint(server=DEFAULT_SERVER, realm=DEFAULT_REALM):
@@ -19,43 +17,24 @@ def get_token_endpoint(server=DEFAULT_SERVER, realm=DEFAULT_REALM):
         server, DEFAULT_REALM_PREFIX.format(realm), DEFAULT_TOKEN_ENDPOINT
     )
 
-
 def get_api_token(
-    client_id, client_secret, target_application, token_endpoint=get_token_endpoint()
+    client_id, client_secret, token_endpoint=get_token_endpoint()
 ):
     logging.debug(
-        "[x] Getting API token as {} for {}".format(client_id, target_application)
-    )
-
-    r = requests.post(
-        token_endpoint,
-        auth=(client_id, client_secret),
-        data={"grant_type": "client_credentials", "audience": target_application},
+        "[x] Getting API token as {} for {}".format(client_id, TARGET_API)
     )
 
-    if not r.ok:
-        logging.error("ERROR getting token: {}".format(r.json()))
-        exit(1)
+    client = OAuth2Session(client_id, client_secret)
+    token = client.fetch_token(token_endpoint, grant_type='client_credentials', audience=TARGET_API)
 
-    response_json = r.json()
-    token = response_json["access_token"]
-    expires_in_seconds = response_json["expires_in"]
-    expiration_datetime = datetime.datetime.now() + datetime.timedelta(
-        seconds=expires_in_seconds
-    )
-
-    logging.debug(jwt.decode(token, verify=False))
     logging.debug("[x] Token obtained")
 
-    return token, expiration_datetime
+    return token["access_token"]
 
 
 parser = argparse.ArgumentParser()
-parser.add_argument("client_id", help="Your client ID")
-parser.add_argument("client_secret", help="Your client secret")
-parser.add_argument(
-    "target_application", help="The client ID for which you want to exchange the token"
-)
+parser.add_argument("--client_id", help="Your client ID")
+parser.add_argument("--client_secret", help="Your client secret")
 parser.add_argument(
     "--realm", help="The keycloak realm, default: cern", type=str, default=DEFAULT_REALM
 )
@@ -70,12 +49,10 @@ if __name__ == "__main__":
     args = parser.parse_args()
     token_endpoint = get_token_endpoint(args.server, args.realm)
     logging.debug(f"[x] Token endpoint: {token_endpoint}")
-    api_token, expiration_datetime = get_api_token(
+    api_token = get_api_token(
         args.client_id,
         args.client_secret,
-        args.target_application,
         token_endpoint=token_endpoint,
     )
     print(api_token)
-    pprint(jwt.decode(api_token, verify=False))
-    print(f"The token expires: {expiration_datetime}")
+    
\ No newline at end of file