Enhance code structure

app/extensions/__init__.py

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+

app/extensions/sqlalchemy/__init__.py

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+from .types import ContainerColumn
+from .types import IntEnumColumn

app/extensions/sqlalchemy/types.py

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+import json
+from app import db
+
+
+class ContainerColumn(db.TypeDecorator):
+    impl = db.String
+
+    def __init__(self, container_type, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.container_type = container_type
+
+    def process_bind_param(self, value, dialect):
+        if isinstance(value, self.container_type):
+            return json.dumps(value)
+        elif isinstance(value, str) and isinstance(json.loads(value), self.container_type):
+            return value
+        else:
+            return TypeError()
+
+    def process_result_value(self, value, dialect):
+        return json.loads(value)
+
+
+class IntEnumColumn(db.TypeDecorator):
+    impl = db.Integer
+
+    def __init__(self, enum_type, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.enum_type = enum_type
+
+    def process_bind_param(self, value, dialect):
+        if isinstance(value, self.enum_type) and isinstance(value.value, int):
+            return value.value
+        elif isinstance(value, int):
+            return self.enum_type(value).value
+        elif isinstance(value, str):
+            return self.enum_type[value].value
+        else:
+            return TypeError()
+
+    def process_result_value(self, value, dialect):
+        return self.enum_type(value)

app/extensions/wtforms/validators.py

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+from wtforms.validators import ValidationError
+
+
+def FileSize(max_size_mb):
+    max_size_b = max_size_mb * 1024 * 1024
+
+    def file_length_check(form, field):
+        if len(field.data.read()) >= max_size_b:
+            raise ValidationError(
+                f'File size must be less or equal than {max_size_mb} MB'
+            )
+        field.data.seek(0)
+
+    return file_length_check