Database Migration Script Writer

**Context**: 
You are a database migration script writer tasked with creating a script to migrate data from an existing legacy database system to a new, modern database system. The legacy system is a relational database management system (RDBMS) with a complex schema, while the new system is a cloud-based NoSQL database. The migration needs to ensure data integrity, consistency, and minimal downtime.

**Detailed Instructions**: 
Write a comprehensive database migration script that performs the following tasks:
1. Connects to the legacy RDBMS and retrieves the schema and data.
2. Transforms the schema to conform to the NoSQL database structure, including any necessary data type conversions and schema modifications.
3. Creates the new schema in the NoSQL database.
4. Migrates the data from the legacy system to the new system, handling any data inconsistencies or errors that may arise during the migration process.
5. Performs data validation and verification to ensure data integrity and consistency.
6. Provides a rollback mechanism in case of migration failures or errors.
7. Documents the migration process, including any assumptions made, data transformations applied, and potential issues encountered.

**Output Format**: 
The output should be a fully executable script written in a programming language of your choice (e.g., Python, Java, SQL), along with a detailed documentation of the migration process. The script should include:
- A header section with comments explaining the purpose of the script, the source and target databases, and any assumptions made.
- A section for connecting to the legacy database and retrieving the schema and data.
- A section for transforming the schema and creating the new schema in the NoSQL database.
- A section for migrating the data and handling any errors or inconsistencies.
- A section for data validation and verification.
- A section for rollback mechanisms.
- A footer section with comments explaining any potential issues encountered during the migration process.

**Examples**: 
For illustration purposes, assume the legacy database has two tables: `customers` and `orders`. The `customers` table has columns `customer_id`, `name`, and `email`, while the `orders` table has columns `order_id`, `customer_id`, `order_date`, and `total`. The NoSQL database has a collection `customers` with fields `customer_id`, `name`, and `email`, and a collection `orders` with fields `order_id`, `customer_id`, `order_date`, and `total`. Provide examples of how the script would handle the migration of these tables, including any necessary data transformations or schema modifications.