Add a flag to modify config.json location

On Kubernetes, it's really awkward to write a Secret into the root directory:

https://www.jeffgeerling.com/blog/2019/mounting-kubernetes-secret-single-file-inside-pod

Therefore this adds support for reading the config from an arbitrary path. The
behaviour is unchanged if you don't set this new flag.

cloudflare-ddns.py

@@ -21,9 +21,6 @@ class GracefulExit:
     print("🛑 Stopping main thread...")
     self.kill_now = True
 
-with open(PATH + "config.json") as config_file:
-    config = json.loads(config_file.read())
-
 def deleteEntries(type):
     # Helper function for deleting A or AAAA records
     # in the case of no IPv4 or IPv6 connection, yet
@@ -70,7 +67,7 @@ def getIPs():
         })
     return ips
 
-def commitRecord(ip):
+def commitRecord(ip, config):
     for c in config["cloudflare"]:
         subdomains = c["subdomains"]
         response = cf_api("zones/" + c['zone_id'], "GET", c)
@@ -143,13 +140,14 @@ def cf_api(endpoint, method, config, headers={}, data=False):
 
     return response.json()
 
-def updateIPs():
+def updateIPs(config):
     for ip in getIPs():
-        commitRecord(ip)
+        commitRecord(ip, config)
 
 if __name__ == '__main__':
     parser = argparse.ArgumentParser()
     parser.add_argument("--repeat", type=bool)
+    parser.add_argument("--config-path", dest="config", type=open, default=os.path.join(PATH, "config.json"))
     args = parser.parse_args()
 
     if args.repeat:
@@ -159,8 +157,8 @@ if __name__ == '__main__':
         killer = GracefulExit()
         while not killer.kill_now:
             time.sleep(max(0, next_time - time.time()))
-            updateIPs()
+            updateIPs(json.load(args.config))
             next_time += (time.time() - next_time) // delay * delay + delay
     else:
-        updateIPs()
+        updateIPs(json.load(args.config))