Add a register api

- Add a register api
- Change requirements, which flask version should be over 2.0

latest version/core/error.py

@@ -0,0 +1,28 @@
+class ArcError(Exception):
+    api_error_code = -999
+    error_code = 108
+    message = None
+
+    def __init__(self, message=None, error_code=None, api_error_code=None) -> None:
+        self.message = message
+        if error_code:
+            self.error_code = error_code
+        if api_error_code:
+            self.api_error_code = api_error_code
+
+    def __str__(self) -> str:
+        return repr(self.message)
+
+
+class InputError(ArcError):
+    def __init__(self, message=None, error_code=None, api_error_code=-100) -> None:
+        super().__init__(message, error_code, api_error_code)
+
+
+class DataExist(ArcError):
+    pass
+
+
+class PostError(ArcError):
+    def __init__(self, message=None, error_code=None, api_error_code=-100) -> None:
+        super().__init__(message, error_code, api_error_code)