add swagger docs to signin and signup endooints

services/backend/api/v1/users/schemas.py

@@ -0,0 +1,20 @@
+from ninja import Schema, ModelSchema
+
+
+from apps.users.models import User
+
+
+class TokenSchema(Schema):
+    token: str
+
+
+class RegisterSchema(ModelSchema):
+    class Meta:
+        model = User
+        fields = ["email", "username", "password"]
+
+
+class LoginSchema(ModelSchema):
+    class Meta:
+        model = User
+        fields = ["email", "password"]