fix: Problem in the description field when using the MariaDB or MySQL.

[MarceloNunesAlves]

This pull request addresses an issue where the 'description' fields, defined as str in the SQLModel model, were being created as varchar(255) columns in MariaDB and MySQL databases. This behavior was inconsistent with the expected text data type for these fields.

Changes:

• Modified the data type of the 'description' fields in the SQLModel model to sqlalchemy.Text. This ensures that the corresponding columns in MariaDB and MySQL are created as text columns, allowing for larger text values.
• Note: PostgreSQL is not affected by this change as it does not require a specific size for text columns.

Reasoning:

• The varchar(255) data type imposes a character limit, which may not be sufficient for storing longer descriptions.
• Using the text data type provides more flexibility for storing variable-length text data without size constraints.