[Enhance] Add limiter & Building API

- Add a custom limiter and use it for limiting users' download instead of using database
> So add a requirement `limits`.

- Fix a character's value
- Change the email max length to 64
- Change something about API's roles and powers
- Add an API endpoint for getting users' roles and powers

latest version/core/limiter.py

@@ -0,0 +1,28 @@
+from limits import parse, strategies
+from limits.storage import storage_from_string
+
+
+class ArcLimiter:
+    storage = storage_from_string("memory://")
+    strategy = strategies.FixedWindowRateLimiter(storage)
+
+    def __init__(self, limit: str = None, namespace: str = None):
+        self._limit = None
+        self.limit = limit
+        self.namespace = namespace
+
+    @property
+    def limit(self):
+        return self._limit
+
+    @limit.setter
+    def limit(self, value):
+        if value is None:
+            return
+        self._limit = parse(value)
+
+    def hit(self, key: str, cost: int = 1) -> bool:
+        return self.strategy.hit(self.limit, self.namespace, key, cost=cost)
+
+    def test(self, key: str) -> bool:
+        return self.strategy.test(self.limit, self.namespace, key)