refactor: add a simple config file to extensions

It makes possible to automagically keep the extensions admin page updated.

lnbits/helpers.py

@@ -1,6 +1,41 @@
 import json
+import os
 import sqlite3
 
+from types import SimpleNamespace
+from typing import List
+
+from .settings import LNBITS_PATH
+
+
+class ExtensionManager:
+    def __init__(self):
+        self._extension_folders: List[str] = [x[1] for x in os.walk(os.path.join(LNBITS_PATH, "extensions"))][0]
+
+    @property
+    def extensions(self) -> List[SimpleNamespace]:
+        output = []
+
+        for extension in self._extension_folders:
+            try:
+                with open(os.path.join(LNBITS_PATH, "extensions", extension, "config.json")) as json_file:
+                    config = json.load(json_file)
+                is_valid = True
+            except Exception:
+                config = {}
+                is_valid = False
+
+            output.append(SimpleNamespace(**{
+                **{
+                    "code": extension,
+                    "is_valid": is_valid,
+                    "path": os.path.join(LNBITS_PATH, "extensions", extension),
+                },
+                **config
+            }))
+
+        return output
+
 
 class MegaEncoder(json.JSONEncoder):
     def default(self, obj):